What city in the US that is not in a state?

Answer 1

That city is Washington, DC. The US Constitution authorized for the creation of a special district to serve as the permanent national capital. The District is therefore not a part of any state. The location selected was a compromise to avoid having the capital in a slave holding or non slave holding state. It was founded in 1790 and is directly overseen by the Federal Government. The District was placed under a single, unified government by an act of Congress in 1871. Officially the District of Columbia, it is unique among American cities because it was established by the Constitution of the United States.

Residents of Washington lack full self government and limited self government was only restored in 1974 after nearly 100 years with an appointed commissioner system. Representation in Congress is limited to a non-voting delegate to the House of Representatives and a shadow Senator. 1964 was the first Presidential election in which Washington residents were able to vote.

A feature of Washington, DC is that it's resident population is around 600,000; except during the average work day, the population is over 1 million.