Why we called Washington D.C ? Why we called this city as District of Colombia?

Question

why we add D.C after the word Washington. what is the connection between Colombia and Washington?

Answer 1

None of the states want to claim the crime infested slum

Answer 2

i think they did it pretty much so people wouldnt confuse Washington D.C. with Washington State which people do all the time. most people from the midwest to the east coast cant even point out washington state on a map