was formally established during the administration of Abraham Lincoln, and was first observed the week following Lincoln's dedication of the Soldier's National Cemetery, where he delivered the Gettysburg Address.
Here is the text of Lincoln's Thanksgiving Day Proclamation from October 3, 1863:
The year that is drawing toward its close has been filled with the blessings of fruitful fields and healthful skies. To these bounties, which are so constantly enjoyed that we are prone to forget the source from which they come, others have been added, which are of so extraordinary a nature that they cannot fail to penetrate and soften the heart which is habitually insensible to the everwatchful providence of almighty God.
In the midst of a civil war of unequaled magnitude and severity, which has sometimes seemed to foreign states to invite and provoke their aggressions, peace has been preserved with all nations, order has been maintained, the laws have been respected and obeyed, and harmony has prevailed everywhere, except in the theater of military conflict; while that theater has been greatly contracted by the advancing armies and navies of the Union.
Needful diversions of wealth and of strength from the fields of peaceful industry to the national defense have not arrested the plow, the shuttle, or the ship; the ax has enlarged the borders of our settlements, and the mines, as well of iron and coal as of the precious metals, have yielded even more abundantly than heretofore. Population has steadily increased, notwithstanding the waste that has been made in the camp, the siege, and the battlefield, and the country, rejoicing in the consciousness of augmented strength and vigor, is permitted to expect continuance of years with large increase of freedom.
No human counsel hath devised, nor hath any mortal hand worked out these great things. They are the gracious gifts of the most high God, who while dealing with us in anger for our sins, hath nevertheless remembered mercy.
It has seemed to me fit and proper that they should be solemnly, reverently, and gratefully acknowledged as with one heart and one voice by the whole American people. I do, therefore, invite my fellow-citizens in every part of the United States, and also those who are at sea and those who are sojourning in foreign lands, to set apart and observe the last Thursday of November next as a day of thanksgiving and praise to our beneficent Father who dwelleth in the heavens. And I recommend to them that, while offering up the ascriptions justly due to him for such singular deliverances and blessings, they do also, with humble penitence for our national perverseness and disobedience, commend to his tender care all those who have become widows, orphans, mourners, or sufferers in the lamentable civil strife in which we are unavoidably engaged, and fervently implore the interposition of the almighty hand to heal the wounds of the nation, and to restore it, as soon as may be consistent with the Divine purposes, to the full enjoyment of peace, harmony, tranquillity, and union.
In testimony whereof, I have hereunto set my hand and caused the seal of the United Stated States to be affixed.