District of Columbia, federal district (2000 pop. 572,059, a 5.7% decrease in population since the 1990 census), 69 sq mi (179 sq km), on the east bank of the Potomac River, coextensive with the city of Washington, D.C. (the capital of the United States). The District was established by congressional acts of 1790 and 1791 and selected by George Washington. It was originally a 10-mi (16.1-km) square (100 sq mi/259 sq km), with Maryland and Virginia granting land on each side of the river, including Georgetown, Md., and Alexandria, Va. The "Federal City" was laid out at its center. Alexandria was returned to Virginia in 1847. The city continued to grow on the east bank of the river and in 1878, when Georgetown became a part of Washington (although it continued to operate as a separate city until 1895), the city of Washington and the District of Columbia became one and the same. Although "Washington" is the name known throughout the world, the city is more commonly called "the District" by its own residents.