George Washington's Thanksgiving Proclamation was given on October 3, 1789. Days of Thanksgiving to God and fasting had been observed in the colonies since their inception, but this was the first Thanksgiving Day observed by the newly born United States of America with its new government and new Constitution. Thanksgiving Day has its roots from a celebration by the Pilgrims of Plymouth Rock in 1621 when they celebrated a bountiful harvest with their Indian friends. Local Indians under the direction of Squanto, an Indian who had traveled in England, and Massasoit, a local chief, had helped the Pilgrims survive with food stores and taught them how to farm the local land and waters. Days of Thanksgiving to God were occasionally proclaimed after George Washington by various presidents, but the holiday didn't become a yearly tradition until 1863 when Abraham Lincoln proclaimed a Day of Thanksgiving. The tradition has remained unbroken ever since, with every President proclaiming a Day of Thanksgiving to God for America's blessings every single year since.
In George Washington's Thanksgiving Proclamation, he states "it is the duty of all Nations to acknowledge the providence of Almighty God, to obey his will, to be grateful for his benefits, and humbly to implore his protection and favor" - an interesting statement in light of the claims by some in modern times that the Founding Fathers were irreligious and wanted a separation of all things religious from any type of government endorsement. Washington states that both houses of Congress had requested him to issue a proclamation asking that all Americans observe a day of thanksgiving and prayer to God and he was responding to this request.
He especially notes that they should express thanks to God for the establishing of their new form of government peacefully. Remember that the Revolutionary War had been over for eight years by this time. The country had been governed by the Articles of Confederation since the end of the war, but the new Constitution was established to overcome the weaknesses of the Articles, and this was done peacefully and without bloodshed.
President Washington asks Americans to thank God for his blessings on the nation, for his divine hand in the recently ended war, for the peace they now have, for civil and religious liberty and prosperity. He also asks them to pray that the government will always be one "of wise, just, and constitutional laws." He ends the proclamation by asking that Americans pray for all nations, especially those that have shown favor to the United States, to be blessed by God with good government, peace, true religion and prosperity.
By the President of the United States of America, a Proclamation.
Whereas it is the duty of all Nations to acknowledge the providence of Almighty God, to obey his will, to be grateful for his benefits, and humbly to implore his protection and favor-- and whereas both Houses of Congress have by their joint Committee requested me to recommend to the People of the United States a day of public thanksgiving and prayer to be observed by acknowledging with grateful hearts the many signal favors of Almighty God especially by affording them an opportunity peaceably to establish a form of government for their safety and happiness.
Now therefore I do recommend and assign Thursday the 26th day of November next to be devoted by the People of these States to the service of that great and glorious Being, who is the beneficent Author of all the good that was, that is, or that will be-- That we may then all unite in rendering unto him our sincere and humble thanks--for his kind care and protection of the People of this Country previous to their becoming a Nation--for the signal and manifold mercies, and the favorable interpositions of his Providence which we experienced in the course and conclusion of the late war--for the great degree of tranquility, union, and plenty, which we have since enjoyed--for the peaceable and rational manner, in which we have been enabled to establish constitutions of government for our safety and happiness, and particularly the national One now lately instituted--for the civil and religious liberty with which we are blessed; and the means we have of acquiring and diffusing useful knowledge; and in general for all the great and various favors which he hath been pleased to confer upon us.
and also that we may then unite in most humbly offering our prayers and supplications to the great Lord and Ruler of Nations and beseech him to pardon our national and other transgressions-- to enable us all, whether in public or private stations, to perform our several and relative duties properly and punctually--to render our national government a blessing to all the people, by constantly being a Government of wise, just, and constitutional laws, discreetly and faithfully executed and obeyed--to protect and guide all Sovereigns and Nations (especially such as have shewn kindness unto us) and to bless them with good government, peace, and concord--To promote the knowledge and practice of true religion and virtue, and the encrease of science among them and us--and generally to grant unto all Mankind such a degree of temporal prosperity as he alone knows to be best.
Given under my hand at the City of New York the third day of October in the year of our Lord 1789.