In 1790, Congress passed the Residence Act which set the capital of the new nation in what then was considered to be the South, in exchange for the Federal government's assumption of the Northern states' war debt.  The legislation was not widely supported, however.  It squeeked through the Senate by only two votes, and narrowly squeezed through the House of Representatives by only two votes.  Had only one Senator or Congressman switched sides, you might be visiting the US Capitol building in Philadelphia or New York City instead of in Washington DC!

Now, we have a blend of what JFK fondly described as "a city of Southern efficiency and Northern charm."

Pennsylvania was opposed to the D.C. site, rather wanting Philadelphia or Trenton, N.J.  Their vote was gathered, however, when they were promised that the main street in D. C. would be named Pennsylvania Ave.