In the United States, the modern Thanksgiving holiday tradition is commonly, but not universally, traced to a sparsely documented 1621 celebration at Plymouth in present-day Massachusetts.
Annual Harvest Festival
The practice of holding an annual harvest festival did not become a regular affair in New England until the late 1660s. Thanksgiving proclamations were made mostly by church leaders in New England up until 1682, and then by both state and church leaders until after the American Revolution. During the revolutionary period, political influences affected the issuance of Thanksgiving proclamations.
Various proclamations were made by royal governors, John Hancock, General George Washington, and the Continental Congress, each giving thanks to God for events favorable to their causes. As President of the United States, George Washington proclaimed the first nationwide thanksgiving celebration in America marking November 26, 1789, “as a day of public thanksgiving and prayer to be observed by acknowledging with grateful hearts the many and signal favours of Almighty God”
Celebrated in all states in 1863
Thanksgiving was first celebrated on the same date by all states in 1863 by a presidential proclamation of Abraham Lincoln. Influenced by the campaigning of author Sarah Josepha Hale, who wrote letters to politicians for around 40 years trying to make it an official holiday, Lincoln proclaimed the date to be the final Thursday in November in an attempt to foster a sense of American unity between the Northern and Southern states. Because of the ongoing Civil War and the Confederate States of America’s refusal to recognize Lincoln’s authority, a nationwide Thanksgiving date was not realized until Reconstruction was completed in the 1870s.
New city of Birmingham observed holiday in 1874
The new city of Birmingham, Alabama celebrated Thanksgiving at the local Episcopal Church November 26, 1874 after the following proclamation by President U. S. Grant. The following was published in the November 26, 1874 newspaper of the Birmingham Iron Age.
We are reminded by the changing seasons that it is time to pause in our daily vocations, and offer thanks to Almighty God for the mercies and abundance of the year which is drawing to a close.
The blessings of free government continue to be vouchsafed to us: the earth has responded in the labor of the husbandman; the land has been free from pestilence; internal order is being maintained, and peace with other powers has prevailed. It is fitting that at stated periods we should cease from our accustomed pursuits and from the turmoil of our daily lives, and unite in thankfulness for the blessings of the past, and in the cultivation of kindly feeling toward each other.
Now therefore, recognizing these considerations, I Ulysses S. Grant, President of the United States, do recommend to all citizens to assemble in their respective places of worship on Thursday, the 26th day of November next, and express their thanks for the mercy and favor of the Almighty God, and laying aside all political contentions and all secular occupations, to observe such a day as a day of praise. In witness whereof, I have herewith set my hand and caused the seal of the United States to be affixed: done at the City of Washington this, the 27th day of October, in the year 1874, and of the Independence of the United States the ninety-ninth.
U. S. Grant
Hamilton Fish, Secretary of State
There will be public service at the Episcopal Church today, in obedience to the proclamation of the President of the United States recommending the observance of this day as an occasion for thanksgiving and praise.
We trust that our people will generally respect the observance. The South should feel a special interest in the present occasion, having met with a new and unexpected deliverance from political oppression.
Note from Wikipedia: The deliverance from political oppression referred to is the Reconstruction era in the South. “Elections to the United States House of Representatives were held in 1874 and 1875 for Representatives to the 44th Congress, occurring in the middle of President Ulysses S. Grant’s second term with a deep economic depression underway. It was an important turning point, as the Republicans lost heavily and the Democrats gained control of the House. It signaled the imminent end of Reconstruction, which Democrats opposed. Historians emphasize the factors of economic depression and attacks on the Grant administration for corruption as key factors in the vote.