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, with Congress holding its first session there in 1800. 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., with over 20 million visitors in 2016.