Although special days of thanksgiving have been common in most religions and cultures for millennia, Thanksgiving in the United States is a uniquely unifying American tradition. Prior to the American Revolution, days of thanksgiving were primarily proclaimed by New England church leaders in response to local or regional abundance. President George Washington designated Nov. 26, 1789, as the first national day of thanksgiving. After 1789, however, thanksgiving observations were carried on as separate state-specific holidays, until President Lincoln established a continuing national observance on the last Thursday of November in 1862 (changed to the fourth Thursday in 1941).
It is a happy coincidence that Thanksgiving quickly follows national (and many state) elections. The holiday quickly displaces the rancor and divisiveness of campaign season with the unity of shared national gratitude and awe.