… is from page 157 of Daniel Boorstin’s wonderful 1973 book, The Americans: The Democratic Experience:
It was [in the late 1930s] a little-known oddity of American life that the United States, unlike other nations, actually had no “national” holidays established by law. Under the federal system the legalizing of holidays had been left to the states. The President’s only power over holidays was to issue proclamations focusing national attention and to give a day off to federal employees in the District of Columbia and elsewhere. Thanksgiving had grown up simply as a national custom. President Lincoln in 1863 was the first to issue a presidential Thanksgiving proclamation, and then the legal holiday was created by separate laws in each of the states.
DBx: Happy Thanksgiving to all of my fellow Americans!