What is the capital city of the United States?

The capital city of the United States is Washington, D.C. This designation is significant because Washington, D.C. was specifically chosen to serve as the nation's capital due to its location and the desire for a neutral ground that was not part of any state. Established in 1790, it is home to the federal government, including the President's residence (the White House), the United States Capitol, and the Supreme Court.

The other cities listed, while being prominent and important urban centers, do not serve as the capital of the nation. New York City, for example, was the first capital under the Constitution but was not designated as the permanent capital. Boston is a historic city known for its role in the American Revolution, and Los Angeles is well-known as the entertainment capital of the world. However, none of these cities holds the political and administrative significance that Washington, D.C. does as the seat of the federal government.