The Patuxent River watershed drains approximately 900 square miles of land. This area includes portions of St. Mary's, Calvert, Charles, Anne Arundel, Prince George's, Howard, and Montgomery Counties. Three main streams drain into the upper Patuxent River: the Little Patuxent, which drains much of the newly urbanized area of Columbia; the Middle Patuxent, which drains agricultural lands in the northern part of its drainage and the outer suburban areas of Columbia in the southern part of its watershed; and the (upper) Patuxent River, which has remained primarily agricultural. Land use in the watershed is mainly forest, with significant urban and agriculture development. Two large metropolitan areas, Baltimore and Washington, D.C., border the Patuxent River, and the watershed has gone through significant suburban development in the past few decades. Columbia and Laurel have developed along the Interstate 95 corridor, which bisects the upper half of the watershed. The 2000 census population for the watershed was 18,000 people. (Based on MD DNR Tributary Strategy Report by Karrh et al., 2007 and updated 2000 land use classifications).