When was Washington D.C. founded?

Founded on July 16, 1790, Washington, DC is unique among American cities because it was established by the Constitution of the United States to serve as the nation’s capital. You can read the actual line at the National Archives. From its beginning, it has been embroiled in political maneuvering, sectional conflicts, and issues of race, national identity, compromise, and, of course, power. Like many decisions in American history, the location of the new city was to be a compromise: Alexander Hamilton and northern states wanted the new federal government to assume Revolutionary War debts, and Thomas Jefferson and southern states wanted the capital placed in a location friendly to slave-holding agricultural interests.

Source: Washington DC