Without Benjamin Banneker, our nation’s capital would not exist as we know it.  After a year of work, the Frenchman hired by George Washington to design the capital, L’Enfant, stormed off the job, taking all the plans.  Banneker, placed on the planning committee at Thomas Jefferson’s request, saved the project by reproducing from memory, in two days, a complete layout of the streets, parks, and major buildings. Thus Washington, D.C. itself can be considered a monument to the genius of this great man.

Source:http://www.bnl.gov/bera/activities/globe/banneker.htm