Washington, D.C.

In 1790, a survey of the land for the District of Columbia was undertaken by Andrew Ellicott with the help of Benjamin Banneker, a free black from Maryland who was a self-taught mathematician and astronomer. Forty boundary stones, laid at one-mile intervals, established the boundaries based on Banneker's celestial calculations.The Potomac River was known to Native Americans as the "Co-hon-ho-roo-ta." The first English explorers called it "Elizabeth."The Residence Bill of July 16, 1790, established a site along the Potomac to be the capital. This federal district was first called the Territory of Columbia and the federal city the City of Washington. The name changed to the District of Columbia in 1793.The most popular museum in DC—and on the planet—is the National Air and Space Museum, which has had 219 million visitors in its first 25 years.DC has 715 libraries—only 118 fewer than New York City.Of adults 25 and older in DC, 42% have at least a bachelor's degree. Washington, DC, is second only to the Silicon Valley, CA region in educational attainment.Compared to the 50 states, DC has the smallest differential between male and female pay in the country.