|Souce: National Archives|
Granted, Thanksgivings were commemorated for nearly 250 years before that and on that Thursday in '63 we were still emmeshed in a Civil War. But ... Lincoln's Proclamation on October 3, 1863 set aside the last Thursday in November as a day of "Thanksgiving and Praise to our beneficient Father who dwelleth in the Heavens". Prior to that, each state set when to observe the holiday. An editor from Godey's Lady Book had been lobbying presidents for almost 20 years for a national holiday and it was Lincoln who complied.
FDR would formally move the holiday up one week in 1939 in a attempt to spur Christmas sales. 1939 would end up with two Thanksgiving days as a result. If Lincoln would have set that day, Thanksgiving would have fallen on the Thursday he delivered the Gettysburg Address! Just thought that was interesting to note.
Above is the first page of Lincoln's proclamation, below, the final two pages. It is commonly accepted that Secretary of State Seward penned the proclamation for Lincoln's signature.
Note: the title is a little deceptive since the proclamation was issued on October 3 and Lincoln's invitation to speak at Gettysburg probably came later (the first Lincoln mentions his plans to attend the event at Gettysburg is October 30). Take it as a writer's perogotive...but it got you to read the blog, didn't it?