Some people are surprised that Washington and Washington DC are actually two different places. Washington is a state that you can find on the Western coast of the United States of America. Washington DC, on the other hand, is located on the Eastern coast of the country. Washington DC is not a state whereas Washington is a state in America.
When you say Washington DC, this means that you have to go to the District of Columbia which is not a part of any state. The District of Columbia is considered to be the capital of the USA even if it is not a part of the 50 states that are listed under America. The reasons for this is they feel that this would have too much power if it becomes a state.