What is the capital city of the United States?

Washington, D.C. is the capital city of the United States because it was established as the nation's capital in 1800, serving as the seat of the federal government. The city was specifically chosen to be on the bank of the Potomac River, between the states of Maryland and Virginia, to provide a neutral ground for the capital that was not part of any existing state, emphasizing its role as a national capital.

Washington, D.C. is unique in that it is not part of any state and has its own local government. It is home to important government institutions, such as the White House, the Capitol, and the Supreme Court, making it the focal point for federal administration and legislation. The significance of Washington, D.C. transcends its geographical location, symbolizing the authority and unity of the national government.

In contrast, New York City, Los Angeles, and Chicago are major urban centers in the United States, known for their cultural, economic, and social contributions, but none serve as the seat of the federal government, which defines the role of the capital city.