Washington, D.C., formally the District of Columbia and also known as D.C. or just Washington, is the capital city of the United States. It is located on the Potomac River bordering Maryland and Virginia. The city was named for George Washington, the first president of the United States and a Founding Father, and the federal district is named after Columbia, a female personification of the nation. As the seat of the U.S. federal government and several international organizations, the city is an important world political capital. It is one of the most visited cities in the U.S., seeing over 20 million visitors in 2016.
The U.S. Constitution provides for a federal district under the exclusive jurisdiction of Congress; the district is therefore not a part of any U.S. state. The signing of the Residence Act on July 16, 1790, approved the creation of a capital district located along the Potomac River near the country's East Coast. The City of Washington was founded in 1791 to serve as the national capital, and Congress held its first session there in 1800. In 1801, the territory, formerly part of Maryland and Virginia, officially became recognized as the federal district.