In 1901, the city proposed the McMillan plan. This plan was to complete L'Enfant's original design for the city. This plan included redesigning and expanding the National Mall. The city continued to expand during the 20th century. The National mall suffered through some riots in the 60's and 70's.
The location of Washington D.C. was a compromise. Alexander Hamilton and northern states wanted the new federal government to assume Revolutionary War debts. Thomas Jefferson and southern states who wanted the capital placed in a location friendly to having slaves. They disagreed and argued a lot. So at the end they compromised.
Washington D.C. was founded on July 16, 1790. Although George Washington oversaw construction of the White House John Adams was the first president to live in the White House. Therefore George never lived in Washington D.C. John Adams lived in the White house from 1791 to 2016 The national mall was in and out of construction. L'Enfant's plan was the reason for some of the reconstruction of the mall.