During Thomas Jefferson's term as Governor of Virginia, the Continental Congress sent a circular to the state executives recommending a day of public thanksgiving.1 Jefferson sent the circular to the Virginia House of Delegates which wrote out the actual proclamation and sent it for his signature.2 Jefferson signed this proclamation for a day of "Thanksgiving and Prayer," to be held on December 9, 1779. At that time, the General Assembly was responsible for formulating state government policies, not the governor. This proclamation did not establish a permanent annual observance.
When Jefferson was President, he expressed some hesitancy to endorse proclamations of this sort. Jefferson wrote in a letter to Reverend Samuel Miller on January 23, 1808, in response to Miller's proposal that he recommend a national day of fasting and prayer: "I consider the government of the United States as interdicted by the Constitution from intermeddling with religious institutions, their doctrines, discipline, or exercises...Certainly no power to prescribe any religious exercise, or to assume authority in religious discipline, has been delegated to the general government. ...But it is only proposed that I should recommend, not prescribe a day of fasting and prayer. That is, that I should indirectly assume to the United States an authority over religious exercises, which the Constitution has directly precluded them from...civil powers alone have been given to the President of the United States and no authority to direct the religious exercises of his constituents."3
National Archives. Legislative Branch: The Center for Legislative Archives. "Congress Establishes Thanksgiving." Provides further historical background on the U.S. government's involvement with the Thanksgiving holiday.