Thanksgiving

The first American Thanksgiving was celebrated, of course, not in Massechussetts in 1621, but two years earlier at Berkely Hundred, Virginia,  4, December, 1619.  In the London company's orders to be opened upon reaching Virginia was this injunction:

" We ordaine that the day of our ships arrivall...In  the land of Virginia shall be yearly and perpetually kept holy as a day of thanksgiving to Almighty God."

That idea they took from the Bible especially Deut. 8:10-20 and Deut. 14: 22-26.

The following Proclamation can be found in Vol. I of the eleven
volume set titled A Compilation of the Messages and Papers of the
Presidents 1789-1908 by James D. Richardson, a representative from
the State of Tennessee, published by Bureau of National Literature
and Art 1908. PROCLAMATION A NATIONAL THANKSGIVING [From Sparks's
Washington, Vol. XII. p. 119.]

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 and 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 in the course and
conclusion of the late war; for the great degree of tranquillity,
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 has 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 shown kindness to us), and to bless them with good governments,
peace, and concord; to promote the knowledge and practice of true
religion and virtue, and the increase 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 3d day of October, A.D. 1789. Go. Washington.