The capital city 

Washington, D.C., is the capital city of the United States, located between Virginia and Maryland on the north bank of the Potomac River. The city is home to all three branches of the federal government, as well as the White House, the Supreme Court and the Capitol Building. More than 500,000 people live in Washington, D.C.

The city of Washington was named for George Washington (who picked the location), while the District of Columbia was named for explorer Christopher Columbus.

Reference from www.history.com/topics/us-states/washington-dc