Counties 20th century Democratic winners were the first Democrats in the 20th century to win without

Another way to gauge re-alignment is to see how many counties a winning presidential nominee is the first nominee of his party (in some period of time) to win without. For example, regarding 1960, Albert J. Menendez noted that '[T]here were 427 counties that supported Roosevelt and Truman five times but refused to support Kennedy. Kennedy was the first Democratic winner to lose these counties in modern times.'

I would use Woodrow Wilson as the relevant signpost for Democratic nominees, as he was the first Democrat elected after the realigning election of 1896. Democrats in the 20th century have often invoked Wilson, but seldom Grover Cleveland, the last Democratic president prior to Wilson (and who, outside the South, had a very different coalition to Wilson). Furthermore, Wilson won narrowly in 1916, so his carrying a county is meaningful immediately (whereas, say, the fact that FDR carried a county in 1932 and 1936 is of little meaning regarding 1940, or even that he carried a county all four times, of little meaning regarding 1948). 

1936 (Counties Franklin Roosevelt was the first Democrat to win without since at least 1892) (44)

Elbert, CO (1964)
Kit Carson, CO
Rio Blanco, CO
Anderson, KS (1976)
Coffey, KS (1964)
Dickinson, KS (1964)
Elk, KS (1964)
Jewell, KS (1964)
Leavenworth, KS (1948) (1992)
Linn, KS (1964)
Miami, KS (1948) (1976) (1992)
Neosho, KS
Norton, KS (1964)
Osage, KS
Phillips, KS (1964)
Republic, KS (1964)
Smith, KS (1964)
Taylor, KY (1948) (1976)
Assumption, LA (1940-1944) (1952) (1960) (1976-1980) (1988-2004)
Carroll, MD
Barry, MO
DeKalb, MO (1976) (1988-1996)
Lafayette, MO (1992-1996)
St Clair, MO (1976) (1992-1996)
Sullivan, MO (1948) (1976) (1992-1996)
Antelope, NE (1964)
Brown, NE (1964)
Furnas, NE (1964)
Hamilton, NE (1964)
Hooker, NE (1964)
Otoe, NE (1964)
Valley, NE (1964)
York, NE (1964)
Adams, OH (1976)
Morrow, OH
Seneca, OH (1996)
Washington, OH
Williams, OH
Wood, OH (1992-1996) (2008-2012)
Clarion, PA
Sullivan, PA
Highland, VA (1964)
Shenandoah, VA (1964)
Crook, WY (1964)

These counties were located in 11 states.

1940 (Counties Franklin Roosevelt was the first Democrat to win without since at least 1892) (251)

Lake, CA (1988-2020)
Adams, CO (1960-1968) (1976) (1988-2020)
Arapahoe, CO (2008-2020)
Archuleta, CO (1960)
Baca, CO (1948)
Bent, CO (1948) (1960) (1976) (1988-2000)
Boulder, CO (1988-2020)
Cheyenne, CO (1948) (1976)
Crowley, CO
Custer, CO
Delta, CO (1948)
Dolores, CO (1948) (1976)
Douglas, CO
Fremont, CO
Garfield, CO (1992) (2020)
Grand, CO
Hinsdale, CO
Jackson, CO
Jefferson, CO (2008-2020)
Kiowa, CO
La Plata, CO (1992) (2004-2020)
Lincoln, CO
Logan, CO
Moffat, CO
Montezuma, CO (1948)
Montrose, CO (1948)
Otero, CO (1948) (1992-1996)
Park, CO
Phillips, CO (1976)
Prowers, CO (1976)
Rio Grande, CO
Saguache, CO (1948) (1960) (1988-2020)
San Juan, CO (1948) (1960) (2004-2020)
Washington, CO (1964)
Weld, CO
Twin Falls, ID (1964)
Adams, IL (1948)
Calhoun, IL (1976) (1988-2008)
Clark, IL (1992)
Clinton, IL (1960) (1992-1996)
Crawford, IL (1992)
Cumberland, IL (1976) (1992)
DeWitt, IL
Edgar, IL (1992)
Fayette, IL (1948) (1976) (1992-1996)
Hamilton, IL (1976) (1992-1996)
Hancock, IL (1988-1996)
Jasper, IL (1992)
Jersey, IL (1948) (1976) (1988-1996)
Lawrence, IL (1992-1996)
Mason, IL (1976) (1992-1996) (2008)
Montgomery, IL (1976) (1988-2000) (2008)
Richland, IL (1992)
Scott, IL
Adams, IN
Boone, IN (1964)
Clay, IN (1948)
Clinton, IN
DeKalb, IN
Franklin, IN
Greene, IN (1948) (1976) (1992)
Huntington, IN
Johnson, IN (1948) (1964)
Marshall IN
Martin, IN (1944-1948) (1976)
Miami, IN
Owen, IN (1976)
Perry, IN (1948) (1960-1968) (1976-1980) (1988-2000) (2008-2012)
Pike, IN (1976-1980) (1992-1996)
Tipton, IN
Whitley, IN
Dubuque, IA (1944-1948) (1960-2012)
Harrison, IA (1948)
Mahaska, IA (1948)
Pottawattamie, IA
Shelby, IA (1948)
Atchison, KS (1976) (1992-1996)
Barton, KS
Bourbon, KS
Chase, KS (1964)
Cloud, KS (1976)
Decatur, KS (1964)
Edwards, KS (1976)
Ellis, KS (1948) (1960) (1976) (1988-1992)
Ford, KS (1948) (1976)
Graham, KS (1964)
Hamilton, KS (1976)
Haskell, KS
Kingman, KS (1976)
Labette, KS (1976) (1992)
Lane, KS
Lincoln, KS (1964)
Lyon, KS
Mitchell, KS (1964)
Morton, KS
Ottawa, KS
Pawnee, KS (1976)
Rawlins, KS (1964)
Rooks, KS (1964)
Rush, KS (1976)
Saline, KS
Scott, KS (1964)
Seward, KS (1964)
Sheridan, KS
Sherman, KS
Stafford, KS (1976)
Stevens, KS
Thomas, KS
Trego, KS
Wichita, KS (1976)
Campbell, KY (1948)
Harford, MD
Talbot, MD (2020)
Cass, MI (1992-1996) (2008)
Monroe, MI (1960-1968) (1976) (1992-2000) (2008-2012)
Le Sueur, MN (1948) (1960-1968) (1976) (1992-1996)
Scott, MN (1948) (1960-1968) (1976-1980) (1992-1996)
Atchison, MO (1948) (1992)
Barton, MO (1948)
Bates, MO (1948) (1976) (1992-1996)
Daviess, MO (1948) (1976) (1992-1996)
Henry, MO (1948) (1976) (1992-1996)
Jasper, MO (1948)
Johnson, MO (1976) (1992)
Livingston, MO (1948) (1976) (1992-1996)
McDonald, MO (1976)
Madison, MO (1948) (1976) (1992-1996)
Newton, MO
Nodaway, MO (1948) (1976) (1988-1996)
Pettis, MO (1948) (1976)
Ste Geneviève, MO (1948) (1960-1968) (1976-1980) (1988-2008)
St François, MO (1948) (1976) (1988-1996)
Texas, MO (1944-1948) (1956) (1976) (1992)
Worth, MO (1948) (1956) (1976) (1988-1996)
Beaverhead, MT (1964)
Adams, NE
Blaine, NE (1964)
Boone, NE
Box Butte, NE (1964)
Buffalo, NE
Cass, NE
Cherry, NE (1964)
Cheyenne, NE (1964)
Clay, NE
Colfax, NE
Custer, NE (1964)
Dawson, NE (1964)
Dodge, NE (1964)
Fillmore, NE
Franklin, NE
Frontier, NE (1964)
Gage, NE
Gosper, NE (1964)
Grant, NE (1964)
Greeley, NE (1944-1948) (1960) (1976)
Harlan, NE (1964)
Hitchcock, NE (1964)
Holt, NE (1964)
Jefferson, NE
Kearney, NE
Keith, NE (1964)
L'Eau Qui Court, NE (1964)
Lincoln, NE
Logan, NE
Merrick, NE (1964)
Nance, NE
Nemaha, NE
Nuckolls, NE
Perkins, NE (1964)
Platte, NE
Polk, NE
Red Willow, NE (1964)
Richardson, NE
Saunders, NE (1948)
Sheridan, NE (1964)
Stanton, NE (1964)
Thomas, NE (1964)
Washington, NE
Webster, NE
Wheeler, NE (1948) (1964)
San Juan, NM
Barnes, ND
Bottineau, ND
Bowman, ND
Cass, ND (2008)
McHenry, ND
McLean, ND (1976)
Pierce, ND (1960) (1976)
Ramsey, ND (1944) (1996)
Stutsman, ND
Towner, ND (1944) (1976) (1988-1996) (2008)
Allen, OH (1964)
Ashland, OH
Auglaize, OH
Clermont, OH
Coshocton, OH (1992)
Crawford, OH
Darke, OH
Defiance, OH
Erie, OH (1992-2012)
Hancock, OH (1964)
Hardin, OH
Henry, OH
Highland, OH
Huron, OH (1996)
Marion, OH
Mercer, OH (1948) (1968)
Monroe, OH (1948) (1968) (1976-2008)
Ottawa, OH (1948) (1976) (1992-1996) (2008-2012)
Preble, OH
Putnam, OH (1948)
Sandusky, OH (1996) (2008-2012)
Shelby, OH (1948)
Wayne, OH
Wyandot, OH
Adair, OK (1948) (1976)
Cherokee, OK (1944-1948) (1976) (1988-2000)
Rogers, OK (1948) (1976)
Tulsa, OK (1964)
Wagoner, OK (1948) (1976)
Washington, OK (1964)
Jackson, OR (1992) (2008)
Linn, OR (1976)
Umatilla, OR (1948)
Adams, PA
Erie, PA (1960-1968) (1976) (1988-2012) (2020)
Fulton, PA
Pike, PA
Aurora, SD (1948) (1956-1976) (1988-1992)
Bennett, SD (1944-1948)
Buffalo, SD (1948) (1956-1976) (1988-2020)
Custer, SD
Hand, SD
Mellette, SD
Pennington, SD
Stanley, SD (1960)
Page, VA (1964)
Rockingham, VA
Adams, WA (1964)
Columbia, WA
Whitman, WA (1964) (1992-1996) (2008) (2016-2020)
Monroe, WV (1976) (1992-1996)
Pleasants, WV (1976) (1992-1996)
Wirt, WV (1976) (1992)
Kewaunee, WI (1960) (1976) (1988-1996) (2008)
La Crosse, WI (1948) (1988-2020)
Sawyer, WI (1976) (1992-1996) (2008-2012)
Waukesha, WI
Campbell, WY (1964)
Fremont, WY
Goshen, WY 

These counties were located in 26 states. 

1944 (102)

Benton, AR (1948) (1964)
Madison, AR (1976) (1992-1996)
Inyo, CA (2020)
Mono, CA (1964) (2004-2020)
San Benito, CA (1992-2020)
Sutter, CA (1964)
Clear Creek, CO (1992-1996) (2004-2020)
Gilpin, CO (1976) (1988-2020)
Mineral, CO (1948) (1960-1968) (1992-1996)
Ouray, CO
Pitkin, CO (1948) (1972) (1988-2020)
Summit, CO (1948) (1992-2020)
Teller, CO (1948)
Lemhi, ID (1964)
Owyhee, ID (1964)
Washington, ID
Effingham, IL (1948)
Moultrie, IL (1976) (1992-1996)
Schuyler, IL (1992-1996) (2008)
Shelby, IL (1948) (1976) (1992-1996)
Wabash, IL
White, IL (1948) (1976) (1992-1996)
Bartholomew, IN (1948)
Cass, IN (1948)
Crawford, IN (1948) (1976) (1992-1996)
Dearborn, IN (1948) (1976)
Gibson, IN (1948) (1976) (1992-1996)
Hancock, IN (1948) (1976)
Harrison, IN (1948) (1976) (1992)
Jackson, IN (1948)
Ohio, IN (1948) (1976)
Posey, IN (1948) (1976) (1992-1996)
Putnam, IN
Shelby, IN (1948)
Washington, IN (1948) (1976) (1992)
Wells, IN (1948)
Fremont, IA
Cherokee, KS (1948) (1976) (1992)
Clark, KS
Fleming, KY (1948) (1976) (1992)
Anne Arundel, MD (2016-2020)
Baltimore County, MD (1992-2020)
Caroline, MD
Frederick, MD (2020)
Howard, MD (1992-2020)
Montgomery, MD (1960-1968) (1976) (1988-2020)
St Mary's, MD (1948) (1960) (1976)
Washington, MD
Worcester, MD
Wilkin, MN (1948) (1976)
Cass, MO (1948) (1976)
Cole, MO (1948) (1964)
Knox, MO (1948) (1976) (1988-1996)
Macon, MO (1948) (1976) (1992-1996)
Vernon, MO (1948) (1976) (1992-1996)
Wayne, MO (1948-1952) (1976) (1992-1996)
Broadwater, MT (1964)
Carbon, MT (1948)
Granite, MT
Madison, MT (1964)
Meagher, MT (1964)
Churchill, NV (1964)
Eureka, NV
Lyon, NV (1964)
Ormsby, NV (2008)
Washoe, NV (2008-2020)
Warren, NJ
Guadalupe, NM (1960) (1976) (1988-2020)
Sierra, NM (1948) (1992-1996)
Union, NM (1948) (1964)
Stanly, NC (1964) (1976)
Brown, OH (1948) (1976)
Fairfield, OH
Hocking, OH (1948) (1976) (1992-1996)
Holmes, OH
Licking, OH
Lucas, OH (1948) (1960-1976) (1988-2020)
Pickaway, OH (1948)
Richland, OH
Ross, OH (1996)
Cimarron, OK (1948) (1964) (1976)
Delaware, OK (1948) (1976) (1992)
Malheur, OR (1964)
Wasco, OR (1960-1968) (1976) (1988-1996) (2008)
Lehigh, PA (1992-2020)
Monroe, PA (2008-2020)
Montour, PA
Bandera, TX
Medina, TX (1948) (1960-1968) (1976)
Grand, UT (1992) (2008) (2020)
Arlington, VA (1976) (1984-2020)
Fairfax, VA (2004-2020)
Madison, VA (1964)
Stafford, VA (1960) (1976) (2020)
Winchester City, VA (2008-2020)
Berkeley, WV (1948)
Lincoln, WV (1948-1968) (1976-2000)
Wood, WV (1948)
Brown, WI (1948) (1960) (1996) (2008)
Manitowoc, WI (1948) (1960-1968) (1976) (1988-1996) (2008)
Park, WY
Platte, WY (1948)

1948 (47)

Butte, CA (1992) (2008) (2020)
Glenn, CA
Mariposa, CA (1976) (1992)
Monterey, CA (1992-2020)
Nevada, CA (2008) (2016-2020)
San Joaquin, CA (1992-1996) (2008-2020)
Tehama, CA (1976) (1992)
Tuolumne, CA (1960) (1976) (1992)
Chaffee, CO (1992-1996) (2012) (2020)
Lake, FL (1964)
Lee, FL (1964)
Manatee, FL (1964)
Orange, FL (1964) (2000-2020)
Palm Beach, FL (1964) (1992-2020)
Pinellas, FL (1992-2000) (2008-2012) (2020)
Dawson, GA (1952-1964) (1976-1980)
Gallatin, MT (1964) (2008) (2016-2020)
Lewis and Clark, MT (1988-1992) (2008)
Humboldt, NV (1960)
Nye, NV (1960) (1976)
Storey, NV (1976)
Burke, NC (1976)
Lincoln, NC (1976)
Eddy, ND (1976) (1996) (2008)
Ward, ND
Coos, OR (1956-1976) (1988-1996)
Columbia, PA (1976) (1996)
Austin, TX
Kerr, TX
Cache, UT (1964)
Washington, UT (1964)
Augusta, VA (1964)
Bath, VA (1976-1980) (1996)
Botetourt, VA (1976)
King George, VA (1960) (1976)
Mathews, VA (1964)
Northumberland, VA (1964)
Pulaski, VA (1976-1980)
Radford City, VA (1976-1980) (1992-1996) (2008-2020)
Richmond County, VA (1964)
Roanoke City, VA (1976-1980) (1988-2020)
Roanoke County, VA (1964)
Rockbridge, VA (1976)
Staunton City, VA (1964) (2008-2020)
Washington, VA
Westmoreland, VA (1976) (1992-1996) (2008-2012)
Williamsburg City, VA (1992-1996) (2004-2020)

(This is excluding Thurmond counties)

These counties were located in 12 states. Thurmond carried at least one county in nine states. Under the probably safe assumption that the vast majority of Thurmond counties were ones that had supported Wilson in 1912 and 1916 and FDR in 1932, 1936, 1940, and 1944, there were probably a total of 18 states containing counties Truman was the first Democrat of the 20th century to win without carrying. Thurmond carried a total of 265 counties, so the total number of counties Truman was the first Democrat in the 20th century to win without is likely close to ~310 (but no more than 312). 

1960 (313)

Apache, AZ (1976) (1984-2020)
Cochise, AZ (1992)
Coconino, AZ (1964) (1992-2020)
Graham, AZ
Maricopa, AZ (1964) (2020)
Mohave, AZ
Navajo, AZ (1964) (1976) (1992-1996)
Yavapai, AZ (1964)
Baxter, AR (1992)
Boone, AR (1976) (1992)
Carroll, AR (1964) (1976) (1992)
Clay, AR (1976-1980) (1988-2004)
Craighead, AR (1976) (1992-2000)
Crawford, AR (1976)
Fulton, AR (1976) (1988-1996)
Garland, AR (1976) (1992-1996)
Independence, AR (1976-1980) (1992-1996)
Marion, AR (1976) (1992-1996)
Montgomery, AR (1976-1980) (1992-1996)
Pike, AR (1976-1980) (1992-1996)
Polk, AR (1976) (1992)
Randolph, AR (1976-1980) (1988-2004)
Scott, AR (1976-1980) (1992-1996)
Sebastian, AR (1964)
Sharp, AR (1976) (1992-1996)
Stone, AR (1976-1980) (1992-1996)
Washington, AR (1976) (1992-1996)
Calaveras, CA
Colusa, CA
Kern, CA
Modoc, CA
Tulare, CA
Yuba, CA (1976)
Eagle, CO (1992-1996) (2004-2020)
Gunnison, CO (1992-1996) (2004-2020)
Mesa, CO
Routt, CO (1992-1996) (2004-2020)
Brevard, FL (1976)
Citrus, FL (1976) (1996)
DeSoto, FL (1964) (1976)
Osceola, FL (1964) (1996-2000) (2008-2020)
Pasco, FL (1976) (1992-2000)
Polk, FL (1964) (1976)
St Lucie, FL (1976) (1996-2012)
Volusia, FL (1976) (1992-2008)
Chatham, GA (1964) (1968) (1976-1980) (1996) (2004-2020)
Gilmer, GA (1964) (1976-1980)
Muscogee, GA (1964) (1976-1980) (1992-2020)
Union, GA (1976-1980)
Whitfield, GA (1976-1980)
Boise, ID
Brown, IL (1976) (1992)
Cass, IL (1976) (1988-1996) (2008)
Greene, IL (1976) (1992-1996)
Jefferson, IL (1976) (1988-1996)
Marion, IL (1976) (1992-1996)
Pike, IL (1976) (1988-1996)
Union, IL (1976) (1992-1996)
Blackford, IN (1976) (1996)
Brown, IN
Knox, IN (1976) (1992-1996)
Madison, IN (1996) (2008)
Scott, IN (1964-1968) (1976-1980) (1992-2000)
Sullivan, IN (1964-1968) (1976) (1988-1996)
Vanderburgh, IN (1992-1996) (2008)
Davis, IA (1976) (1984-1996)
Decatur, IA (1976) (1988-1996)
Jasper, IA (1976) (1988-1996) (2004-2012)
Johnson, IA (1964-2020)
Marion, IA (1976) (1988)
Monona, IA (1976) (1988-1996)
Barren, KY (1976) (1992)
Boone, KY
Boyle, KY (1976-1980)
Bracken, KY (1976-1980) (1992)
Bullitt, KY (1976) (1992)
Clark, KY (1976-1980) (1992-1996)
Daviess, KY (1976-1980) (1992)
Fayette, KY (1996) (2008-2020)
Grant, KY (1976-1980)
Hardin, KY (1976)
Hart, KY (1976) (1992)
Jefferson, KY (1992-2020)
Jessamine, KY
Kenton, KY
LaRue, KY (1976-1980) (1992)
Lincoln, KY (1976)
Livingston, KY (1964-1968) (1976-1996)
Madison, KY (1976)
Mason, KY (1964-1968) (1976-1980) (1992)
McLean, KY (1964-1968) (1976-1980) (1988-1996)
Mercer, KY (1976-1980)
Oldham, KY
Pendleton, KY (1976-1980)
Powell, KY (1976-1980) (1992-1996)
Spencer, KY (1976-1980) (1992)
Warren, KY (1976)
Woodford, KY (1976-1980)
Cecil, MD (1976)
Kent, MD (1976-1980) (1996) (2008) (2020)
Wicomico, MD
Hennepin, MN (1964-1968) (1976-2020)
Buchanan, MO (1976-1980) (1988-2000) (2008)
Carter, MO (1976) (1992)
Clay, MO (1976) (1992-2000)
Clinton, MO (1976) (1988-1996)
Dent, MO (1976) (1992)
Dunklin, MO (1964-1968) (1976-1980) (1988-1996)
Gentry, MO (1976) (1988-1996)
Iron, MO (1964-1968) (1976-1980) (1988-1996)
Linn, MO (1964-1968) (1976) (1988-1996)
Oregon, MO (1964-1968) (1976-1996)
Phelps, MO (1976) (1992)
Pulaski, MO (1976) (1992)
Reynolds, MO (1964-1968) (1976-1996)
Ripley, MO (1976) (1992-1996)
Saline, MO (1976) (1988-2000)
Schuyler, MO (1976) (1992-1996)
Scotland, MO (1976) (1992-1996)
Shannon, MO (1964-1968) (1976-1980) (1988-1996)
Stoddard, MO (1976) (1992)
Fergus, MT
Jefferson, MT (1964-1968)
Sanders, MT (1992)
Dakota, NE (1988) (1996)
Douglas, NE (2008) (2016-2020)
Howard, NE
Sarpy, NE
Thurston, NE (1988) (1996) (2004-2012)
Chaves, NM
Curry, NM
Quay, NM (1976)
Roosevelt, NM
Alamance, NC (1976)
Buncombe, NC (1976) (1992-1996) (2008-2020)
Caldwell, NC (1976)
Forsyth, NC (1976) (2008-2020)
Gaston, NC (1976)
Graham, NC (1976)
Guilford, NC (1976) (1992-1996) (2004-2020)
Haywood, NC (1976-1980) (1988-1996)
Iredell, NC (1964) (1976)
Jackson, NC (1976-1980) (1992-1996) (2008)
McDowell, NC (1976)
Macon, NC (1976)
Mecklenburg, NC (1976) (1996) (2004-2020)
Montgomery, NC (1976-1980) (1992-1996)
Moore, NC
Rowan, NC (1976)
Rutherford, NC (1976)
Foster, ND (1976)
Grand Forks, ND (2008)
McKenzie, ND
Walsh, ND (1976)
Butler, OH
Montgomery, OH (1964-1968) (1976-1980) (1992-2012) (2020)
Portage, OH (1964-1968) (1976) (1992-2012)
Tuscarawas, OH (1964-1968) (1976) (1992-1996) (2008)
Atoka, OK (1976-1980) (1988-1996)
Beckham, OK (1976) (1992)
Caddo, OK (1976) (1988-1996)
Canadian, OK
Cleveland, OK
Comanche, OK
Craig, OK (1976) (1988-1996)
Custer, OK
Garvin, OK (1964-1968) (1976) (1988-1996)
Grady, OK (1964-1968) (1976)
Greer, OK (1964-1968) (1976) (1988-1996)
Haskell, OK (1964-1968) (1976-2000)
Hughes, OK (1964-1968) (1976-2000)
Kiowa, OK (1976) (1988-1996)
Le Flore, OK (1964-1968) (1976) (1992-1996)
McClain, OK (1976)
McIntosh, OK (1964-1968) (1976-1980) (1988-2000)
Mayes, OK (1976) (1988-1996)
Muskogee, OK (1964-1968) (1976-1980) (1988-2000)
Okfuskee, OK (1964-1968) (1976-1980) (1988-1996)
Oklahoma, OK
Osage, OK (1976) (1988-1996)
Ottawa, OK (1976) (1988-2000)
Pontotoc, OK (1964-1968) (1976) (1992-1996)
Pottawatomie, OK (1976)
Roger Mills, OK (1976)
Seminole, OK (1964-1968) (1976) (1988-1996)
Sequoyah, OK (1976) (1992-1996)
Stephens, OK (1976) (1992)
Texas, OK (1964)
Washita, OK (1976) (1992)
Harney, OR
Klamath, OR
Lake, OR
Berks, PA (2008)
York, PA
Brown, SD (1964-1976) (1988-1996) (2008)
Chester, TN (1976)
Clay, TN (1976-1980) (1992-2004)
Crockett, TN (1964) (1976-1980) (1992-2000)
Dyer, TN (1976-1980) (1992-1996)
Madison, TN (1964) (1976)
Sullivan, TN (1976)
Anderson, TX (1964-1968) (1976)
Armstrong, TX (1976)
Brazoria, TX (1964-1968) (1976)
Brewster, TX (1964-1968) (1992-1996) (2008)
Childress, TX (1964-1968) (1976)
Coleman, TX (1976) (1992)
Collingsworth, TX (1964-1968) (1976)
Cooke, TX
Crockett, TX (1964-1968) (1976) (1992)
Dallam, TX (1976)
Dallas, TX (2008-2020)
Dawson, TX
Deaf Smith, TX
Denton, TX
Donley, TX (1976)
Eastland, TX (1964-1968) (1976)
Ector, TX (1964)
Edwards, TX (1964)
Erath, TX (1964-1968) (1976-1980)
Floyd, TX (1976)
Gaines, TX (1976)
Goliad, TX (1976)
Gray, TX (1964)
Gregg, TX (1964)
Hale, TX (1976)
Hamilton, TX (1976)
Hansford, TX (1964)
Hardeman, TX (1964-1968) (1976-1980) (1988-1996)
Harris, TX (2008-2020)
Hartley, TX
Hemphill, TX
Hutchinson, TX (1964)
Jack, TX (1964-1968) (1976) (1992)
Johnson, TX (1964-1968) (1976)
Kimble, TX
Lipscomb, TX (1964)
Live Oak, TX (1976)
Lubbock, TX
McMullen, TX
Mason, TX (1976)
Matagorda, TX (1964-1968) (1976)
Menard, TX (1976) (1988-1996)
Midland, TX (1964)
Mills, TX (1964-1968) (1976-1980) (1992)
Moore, TX (1976)
Motley, TX (1976)
Ochiltree, TX (1964)
Panola, TX (1964) (1976) (1992-1996)
Parmer, TX (1976)
Potter, TX
Randall, TX (1964)
Roberts, TX (1964)
Runnels, TX
Rusk, TX
Schleicher, TX
Sherman, TX (1964) (1976)
Smith, TX (1964)
Somervell, TX (1964-1968) (1976-1980)
Stephens, TX (1976)
Tarrant, TX (2020)
Taylor, TX
Tom Green, TX
Tyler, TX (1976-1980) (1988-1996)
Uvalde, TX
Waller, TX (1964-1968) (1976-1980) (1988-1996)
Wheeler, TX (1976)
Wilbarger, TX (1964-1968) (1976)
Wise, TX (1964-1968) (1976-1980)
Yoakum, TX
Zavala, TX (1964-1968) (1976-2020)
Utah, UT
Albemarle, VA (1964) (2004-2020)
Amelia, VA (1964) (1976)
Bristol City, VA (1976)
Buena Vista City, VA (1976-1980) (1992-1996)
Charles River, VA
Charlottesville City, VA (1976-2020)
Chesterfield, VA (1964) (2020)
Clifton Forge City, VA (1976-1980) (1988-2000) (defunct after 2000)
Culpeper, VA
Cumberland, VA (1964) (1968) (1976)
Danville City, VA (1964) (2004-2020)
Essex, VA (1964) (1968) (1996) (2008-2012)
Fauquier, VA
Fluvanna, VA (1976)
Frederick, VA
Fredericksburg City, VA (1976) (1992-2020)
Gloucester, VA (1976)
Hampton City, VA (1964-1968) (1976-1980) (1992-2020)
Hanover, VA (1964)
Henrico, VA (1964) (2008-2020)
James City County, VA (1964-1968) (2020)
King William, VA (1964)
Lancaster, VA (1964)
Loudoun, VA (2008-2020)
Lynchburg City, VA (1964) (2020)
Middlesex, VA (1964)
New Kent, VA (1964-1968) (1976)
Newport News City, VA (1964-1968) (1976) (1996-2020)
Orange, VA (1964)
Powhatan, VA (1964) (1968)
Prince Edward, VA (1964) (1996) (2004-2020)
Richmond City, VA (1964-1968) (1976-2020)
Douglas, WA
Stevens, WA
Cabell, WV (1976) (1992-1996)
Kanawha, WV (1964-1968) (1976-1980) (1988-2000)
Wetzel, WV (1976-1980) (1988-1996)
Langlade, WI (1996) (2008)
Albany, WY (1992-1996) (2008) (2020)
Hot Springs, WY
Sheridan, WY

There were 313 counties which Kennedy was the first Democrat to win in the 20th century without carrying (obviously a subset of the 427 counties Kennedy was the first Democrat in the prior 30 years to win without carrying), located in 32 states. This means that there were more counties Kennedy was the first Democrat in the 20th century to win without than Truman in 1948 even if every single Thurmond county had voted Democratic in 1912, 1916, 1932, 1936, 1940, and 1944 (which the vast majority almost certainly did, but not all--for example, Chilton, Cullman, and Shelby, AL; and Assumption and Lafourche, LA, did not). And, even counting the Thurmond counties 'against' Truman, the counties Kennedy was the first Democrat of the 20th century to win without carrying were spread out over far more states.