National New York Day is observed annually on September 21, celebrating New York State's significance as the 11th state to ratify the U.S. Constitution and join the Union. Established in 2017 by National Day Calendar, this day honors the state's rich history, including its early inhabitants such as the Iroquois and Algonquian tribes, and its pivotal role during the American Revolution, where many battles were fought, including the Battle of Long Island. New York City was also designated as the national capital from 1785 until 1790. The day is part of the National State Days project, which celebrates each state in the order they joined the Union. While it is not an official holiday, it serves as a reminder of New York's contributions to American history and culture.