A federal judge in Wisconsin has ruled that Thanksgiving Day has been unconstitutional since it originated with President George Washington’s proclamation in 1789.
Noting that Congress had “recommend to the people of the United States a day of public thanksgiving and prayer,” Washington declared that Thursday, Nov. 26, should be devoted to giving sincere and humble thanks to the “great and glorious Being who is the beneficent author of all the good that was, that is, or that will be …”
Ruling in a suit brought by the Freedom From Religion Foundation, U.S. District Judge Barbara Crabb said: “It is because the nature of prayer is so personal and can have such a powerful effect on a community that the government may not use its authority to try to influence an individual’s decision whether and when to pray.”
Crabb, appointed to the federal bench by President Jimmy Carter in 1979, added that Washington’s proclamation “goes beyond mere ‘acknowledgment’ of religion because its sole purpose is to encourage all citizens to engage in prayer, an inherently religious exercise that serves no secular function in this context. In this instance, the government has taken sides on a matter that must be left to individual conscience.”
Federal judge, holiday, prayer, unconstitutional

Wenceslaus
Federal Judge Barbara Crabb did not rule that Thanksgiving is unconstitutional. To the contrary, she wrote in her decision in Freedom From Religion Foundation, Inc. v. Obama:
Sometimes a statute that may seem at first blush to promote a religious belief may survive scrutiny under the establishment clause if the benefit to religion is incidental and the government has a valid secular purpose for its conduct. Metzl v. Leininger, 57 F.3d 618, 620 (7th Cir.1995) (“[A] law that promotes religion may nevertheless be upheld either because of the secular purposes that the law also serves or because the effect in promoting religion is too attenuated to worry about.”). For example, in McGowan v. Maryland, 366 U.S. 420 (1961), the Court upheld a state’s Sunday closing law because many employees would prefer not to work on Sunday regardless of their religion. Other commonly cited examples are the national observances of Christmas and Thanksgiving. E.g., Lynch, 465 U.S. at 675. Although these holidays have religious origins, their celebration by the government does not connote endorsement in the eyes of the reasonable observer because of the significant secular meaning the holidays now have. Metzl, 57 F.3d at 620.