Washington D.C. is the capital of the US whose area covers the District of Columbia. Washington state is a state in the northwestern US.
The signing of the Residence Act on July 16, 1790, approved the creation of a capital district located along the Potomac River on the country's East Coast. The states of Maryland and Virginia each donated land to form the federal district. As permitted by the U.S. Constitution, the District is under the exclusive jurisdiction of the United States Congress and is therefore not a part of any U.S. state.

The United States of America (USA or U.S.A.) is commonly referred to as the United States (US or U.S.), America, or simply the States. It is a federal republic.

The USA has 50 states and one federal district, the federal district of Washington, D.C. There are 48 contiguous states between Canada and Mexico, plus the state of Alaska and the state of Hawaii.