-- M. J. Dubin : United States Presidential Elections, 1788-1860
-- W. D. Burnham : Presidential Ballots, 1836-1892
-- E. E. Robinson : The Presidential Vote : 1896 to 1932
-- R. M. Scammon : America at the Polls (1920-1964)
-- R. M. Scammon : America at the Polls (1968-1984)
-- R. M. Scammon / A. McGillivray : America Votes n° 18, 1988; n° 20, 1992; n° 22, 1996; n° 24, 2000
Plus:
-- Various almanacs to complete MM. Dubin, Burnham and Robinson, especially The Chicago Daily News Almanac.
      Indeed, these publications sometimes made mistakes when copying the documents they had, which is human but harmful. Either by making a mistake on an isolated number, or by inverting the results of two consecutive counties, or even by getting the wrong candidate. Moreover, it should be noted that all these authors except Robinson chose, when they had the detailed results of the lists of electors, the one who came first in the State, whereas the almanacs and most often the official publications chose the head of list, and therefore resulted in sometimes slightly lower figures.
And since 2004:
-- Secretary of state for all states and all ballots.

-- Electoral returns by counties and datas of the Bureau of the Census regarding 1880, 1920, 1960, 2000 and 2010.