
Which individual can be said to be credited with the formation of the national capital city of Washington DC
It was James Madison the fourth President of the US who stressed the need for a federal district on January 23, 1788, in his Federal papers that he wrote, in the "Federalist No 43" to be precise.
He argued that the national capital needed to be separate from the states so that its safety and maintenance was not compromised. He is also called the Father of the Constitution.
http://www.american-presidents.com/james-madison

