On what date did the United States celebrate its first national Thanksgiving in 1777?

The United States celebrated its first national Thanksgiving on December 18, 1777.

The Continental Congress designated the day after the American victory at Saratoga. The proclamation called on the states to set aside Thursday, December 18, for thanksgiving and praise, linking the observance to military success and hopes for independence and peace.

This event occurred during the Revolutionary War, when Congress served as the national government and met temporarily in York, Pennsylvania, because British forces occupied Philadelphia. It was not the modern federal holiday established by later legislation and presidential proclamations.

George Washington issued the first presidential Thanksgiving proclamation in 1789, setting November 26 as a day of public thanksgiving and prayer. The modern national holiday developed through later nineteenth-century practice and was standardized by federal law in 1941, making the 1777 observance an important early predecessor rather than the current holiday.