Which city is the capital of the United States of America?

Washington D.C. is the capital of the United States of America because it was specifically established as a federal district under the United States Constitution. In 1789, the U.S. Congress designated this specific area along the Potomac River to serve as the seat of the federal government. The Founding Fathers wanted a neutral and independent location for the capital, separate from individual states, in order to avoid favoring any particular region or state. Thus, Washington D.C. was chosen, and it has remained the political center of the country ever since.