Biggest county map changes in elections

[Del Tachi]

In 1972, all of the counties in Georgia voted for Richard Nixon.  Four years later in 1976, they all voted for Democrat Jimmy Carter. 

Any other such examples of such big county swaps/flips occurring over only one election cycle?

[RI]

Post Civil War, states where 100% of counties went one party then 100% for the opposite party next election:

Delaware 1892-1896
Idaho 1892-1896* (100% non-D to 100% D)
Nevada 1892-1896* (100% non-D to 100% D)
Nevada 1900-1904
Delaware 1908-1912
Maine 1908-1912* (100% R to 100% non-R)
Utah 1916-1920
Mississippi 1944-1948
Delaware 1964-1968
Mississippi 1964-1968* (100% non-R to 100% R)
Hawaii 1968-1972
Delaware 1972-1976
Georgia 1972-1976
Hawaii 1972-1976
Delaware 1976-1980
Hawaii 1984-1988
Maine 1988-1992* (100% R to 100% non-R)

In general, 1916-1920 probably had close to the highest number of county flips ever. 1928-1932 saw a lot too, maybe more, but Al Smith actually did pretty well in winning isolated counties in almost every state out west.