There was a much bigger list on wikipedia of bellwether counties (though it has since been edited to remove them). They were not quite as accurate as the ones above, but still were on the wrong side only three times in half a century or more. I checked each of them out.
Michigan (Trump wins all 35! Usually huge margins.)
Bay County – Trump 57.8%
Calhoun County – Trump 54.8%
Eaton County – Trump 49.5%
Manistee County – Trump 56.8%
Isabella County – Trump 50.4%
Macomb County – Trump 53.3%
Monroe County – Trump 60.5%
Shiawassee County – Trump 59%
Van Buren County – Trump 55.3%
Delta County – Trump 62.4%
St. Clair County – Trump 64.3%
Benzie County – Trump 53.8%
Houghton County – Trump 56.1%
Lenawee County – Trump 59.1%
Alcona County – Trump 68.6%
Alpena County – Trump 63%
Cass County – Trump 63.7%
Cheboygan County – Trump 64.2%
Clare County – Trump 66.7%
Crawford County – Trump 64.6%
Dickinson County Trump 64%
Gladwin County – Trump 67.7%
Gratiot County – Trump 63.3%
Iosco County – Trump 63.5%
Kalkaska County – Trump 70%
Luce County – Trump 70.3%
Mackinac County – Trump 61.5%
Mason County – Trump 59.2%
Mecosta County – Trump 63%
Menominee County – Trump 64.4%
Ogemaw County – Trump 69.3%
Ontonagon County – Trump 62%
Presque Isle County – Trump 64%
Roscommon County – Trump 64.4%
Schoolcraft County – Trump 65.1%
Wisconsin (Trump wins 28 of 30! Usually by huge margins and the 2 that went Biden were razor thin)
Sauk County – Biden 50%
Price County – Trump 62.4%
Chippewa County – Trump 59.4%
Marquette County – Trump 63.2%
Lincoln County – Trump 60.7%
Winnebago County – Trump 51%
Racine County – Trump 51.3%
Forest County – Trump 65.1%
Door County – Biden 50%
Columbia County – Trump 50%
Grant County – Trump 55.2%
Crawford County – Trump 53.1%
Richland County – Trump 54.2%
Lafayette County – Trump 56.4%
Brown County – Trump 52.8%
Jackson County – Trump 56.9%
Outagamie County – Trump 54.1%
Trempealeau County – Trump 57.5%
Jefferson County – Trump 56.9%
Wood County – Trump 59%
Oneida County – Trump 56.7%
Barron County – Trump 62.4%
Manitowoc County – Trump 60.8%
Washburn County – Trump 61.2%
Monroe County – Trump 61.1%
Marathon County – Trump 58.3%
Kewaunee County – Trump 65.7%
Clark County – Trump 67.3%
Rusk County – Trump 66.7%
Oconto County – Trump 69.9%
Minnesota (Trump wins of 14 of 18! Usually by huge margins, while the 4 that went for Biden were all razor thin)
Stevens County – Trump 60.1%
Chippewa County – Trump 64.4%
Watonwan County – Trump 59.8%
Houston County – Trump 55.5%
Traverse County – Trump 62.9%
Kittson County – Trump 58.8%
Nicollet County – Biden 50.5%
Clay County – Biden 50.9%
Blue Earth County – Biden 51%
Winona County – Biden 49.2%
Pope County – Trump 63%
Grant County – Trump 62.2%
Yellow Medicine County – Trump 67.8%
Lincoln County – Trump 68.1%
Pennington County – Trump 62.4%
Le Sueur County – Trump 64.2%
Murray County – Trump 68.9%
Benton County – Trump 64.7%
Pennsylvania (Trump wins all 5!)
Luzerne County – Trump 56.8%
Carbon County – Trump 65.4%
Elk County – Trump 71.8%
Warren County – Trump 68.9%
Clinton County – Trump 67.5%
Virginia (Trump wins 7 of 8! Half by a huge margin and half by a good clip, but the one Biden gets is razor thin)
Buckingham County – Trump 56.1%
Nelson County – Trump 51.4%
Essex County – Trump 49.9%
Montgomery County – Biden 51.8%
King and Queen County – Trump 59.7%
Alleghany County – Trump 71.7%
Tazewell County – Trump 83.4%
Giles County – Trump 75.1%
North Carolina (Trump wins of 9 of 18! This is what a legitimately close election looks like.)
Granville County – Trump 52.8%
Martin County – Trump 52.1%
Pitt County – Biden 54.1%
Forsyth County – Biden 56.3%
Wilson County – Biden 51%
Wake County – Biden 62.5%
Buncombe County – Biden 59.9%
Guilford County – Biden 61%
Cumberland County – Biden 57.5%
Mecklenburg County – Biden 66.9%
Watauga County – Biden 53.3%
Jackson County – Trump 53.1%
Hyde County – Trump 57.1%
Franklin County – Trump 56.1%
Perquimans County – Trump 65.6%
Montgomery County – Trump 65.5%
Madison County – Trump 61.2%
Camden County – Trump 72.8%
Georgia (Trump wins 15 of 20!)
Newton County – Biden 54.9%
Douglas County – Biden 62%
Early County – Trump 52.4%
Baldwin County – Biden 50.1%
Sumter County – Biden 52%
Burke County – Trump 50.5%
Rockdale County – Biden 69.9%
Chattahoochee County – Trump 55.6%
Wheeler County – Trump 69.3%
Butts County – Trump 71.4%
Heard County – Trump 83.8%
Polk County – Trump 78.1%
Long County – Trump 62.4%
Hart County – Trump 74.4%
Chattooga County – Trump 80.2%
Elbert County – Trump 67.9%
Treutlen County – Trump 68.3%
Decatur County – Trump 58.1%
Screven County – Trump 59.1%
Wilkes County – Trump 56.1%
**Arizona **(Trump wins all 3, but there are so few counties in the state that I don't know how much this can tell us)
There was a much bigger list on wikipedia of bellwether counties (though it has since been edited to remove them). They were not quite as accurate as the ones above, but still were on the wrong side only three times in half a century or more. I checked each of them out.
Michigan (Trump wins all 35! Usually huge margins.)
Bay County – Trump 57.8%
Calhoun County – Trump 54.8%
Eaton County – Trump 49.5%
Manistee County – Trump 56.8%
Isabella County – Trump 50.4%
Macomb County – Trump 53.3%
Monroe County – Trump 60.5%
Shiawassee County – Trump 59%
Van Buren County – Trump 55.3%
Delta County – Trump 62.4%
St. Clair County – Trump 64.3%
Benzie County – Trump 53.8%
Houghton County – Trump 56.1%
Lenawee County – Trump 59.1%
Alcona County – Trump 68.6%
Alpena County – Trump 63%
Cass County – Trump 63.7%
Cheboygan County – Trump 64.2%
Clare County – Trump 66.7%
Crawford County – Trump 64.6%
Dickinson County Trump 64%
Gladwin County – Trump 67.7%
Gratiot County – Trump 63.3%
Iosco County – Trump 63.5%
Kalkaska County – Trump 70%
Luce County – Trump 70.3%
Mackinac County – Trump 61.5%
Mason County – Trump 59.2%
Mecosta County – Trump 63%
Menominee County – Trump 64.4%
Ogemaw County – Trump 69.3%
Ontonagon County – Trump 62%
Presque Isle County – Trump 64%
Roscommon County – Trump 64.4%
Schoolcraft County – Trump 65.1%
Wisconsin (Trump wins 28 of 30! Usually by huge margins and the 2 that went Biden were razor thin)
Sauk County – Biden 50%
Price County – Trump 62.4%
Chippewa County – Trump 59.4%
Marquette County – Trump 63.2%
Lincoln County – Trump 60.7%
Winnebago County – Trump 51%
Racine County – Trump 51.3%
Forest County – Trump 65.1%
Door County – Biden 50%
Columbia County – Trump 50%
Grant County – Trump 55.2%
Crawford County – Trump 53.1%
Richland County – Trump 54.2%
Lafayette County – Trump 56.4%
Brown County – Trump 52.8%
Jackson County – Trump 56.9%
Outagamie County – Trump 54.1%
Trempealeau County – Trump 57.5%
Jefferson County – Trump 56.9%
Wood County – Trump 59%
Oneida County – Trump 56.7%
Barron County – Trump 62.4%
Manitowoc County – Trump 60.8%
Washburn County – Trump 61.2%
Monroe County – Trump 61.1%
Marathon County – Trump 58.3%
Kewaunee County – Trump 65.7%
Clark County – Trump 67.3%
Rusk County – Trump 66.7%
Oconto County – Trump 69.9%
Minnesota (Trump wins of 14 of 18! Usually by huge margins, while the 4 that went for Biden were all razor thin)
Stevens County – Trump 60.1%
Chippewa County – Trump 64.4%
Watonwan County – Trump 59.8%
Houston County – Trump 55.5%
Traverse County – Trump 62.9%
Kittson County – Trump 58.8%
Nicollet County – Biden 50.5%
Clay County – Biden 50.9%
Blue Earth County – Biden 51%
Winona County – Biden 49.2%
Pope County – Trump 63%
Grant County – Trump 62.2%
Yellow Medicine County – Trump 67.8%
Lincoln County – Trump 68.1%
Pennington County – Trump 62.4%
Le Sueur County – Trump 64.2%
Murray County – Trump 68.9%
Benton County – Trump 64.7%
Pennsylvania (Trump wins all 5!)
Luzerne County – Trump 56.8%
Carbon County – Trump 65.4%
Elk County – Trump 71.8%
Warren County – Trump 68.9%
Clinton County – Trump 67.5%
Virginia (Trump wins 7 of 8! Half by a huge margin and half by a good clip, but the one Biden gets is razor thin)
Buckingham County – Trump 56.1%
Nelson County – Trump 51.4%
Essex County – Trump 49.9%
Montgomery County – Biden 51.8%
King and Queen County – Trump 59.7%
Alleghany County – Trump 71.7%
Tazewell County – Trump 83.4%
Giles County – Trump 75.1%
North Carolina (Trump wins of 9 of 18! This is what a legitimately close election looks like.)
Granville County – Trump 52.8%
Martin County – Trump 52.1%
Pitt County – Biden 54.1%
Forsyth County – Biden 56.3%
Wilson County – Biden 51%
Wake County – Biden 62.5%
Buncombe County – Biden 59.9%
Guilford County – Biden 61%
Cumberland County – Biden 57.5%
Mecklenburg County – Biden 66.9%
Watauga County – Biden 53.3%
Jackson County – Trump 53.1%
Hyde County – Trump 57.1%
Franklin County – Trump 56.1%
Perquimans County – Trump 65.6%
Montgomery County – Trump 65.5%
Madison County – Trump 61.2%
Camden County – Trump 72.8%
Georgia (Trump wins 15 of 20!)
Newton County – Biden 54.9%
Douglas County – Biden 62%
Early County – Trump 52.4%
Baldwin County – Biden 50.1%
Sumter County – Biden 52%
Burke County – Trump 50.5%
Rockdale County – Biden 69.9%
Chattahoochee County – Trump 55.6%
Wheeler County – Trump 69.3%
Butts County – Trump 71.4%
Heard County – Trump 83.8%
Polk County – Trump 78.1%
Long County – Trump 62.4%
Hart County – Trump 74.4%
Chattooga County – Trump 80.2%
Elbert County – Trump 67.9%
Treutlen County – Trump 68.3%
Decatur County – Trump 58.1%
Screven County – Trump 59.1%
Wilkes County – Trump 56.1%
**Arizona **(Trump wins all 3, but there are so few counties in the state that I don't know how much this can tell us)
Gila County – Trump 66.4%
Pinal County – Trump 56.8%
Navajo County – Trump 53.4%
Nevada
None