Proclamation of a Day of Thanksgiving, 1789
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.
...Therefore, I recommend and assign (a day) 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 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 signs and manifold mercies and the favorable interpositions of His providence; for the great degree of tranquility, union, and plenty, which we have enjoyed; for the peaceable and rational manner in which we have been enabled to establish constitutions of government for our safety and happiness; 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.
Note: During his first year in office, President Washington introduced the practice ("duty") of issuing an executive proclamation urging nationwide prayer and thanksgiving.