The United States National Arboretum is an arboretum in northeast Washington, D.C., operated by the United States Department of Agriculture's Agricultural Research Service. It was established in 1927 by an act of Congress after a campaign by USDA Chief Botanist Frederick Vernon Coville. It is 446 acres (1.80 km2) in size and is located 2.2 miles (3.5 km) northeast of the Capitol building, with entrances on New York Avenue, NE and R Street, NE. The campus's gardens, collections, and features are connected by roadways that are 9.5 miles (15.3 km) long in total. In addition to the main campus in Washington, D.C., there are research locations at the Henry A. Wallace Beltsville Agricultural Research Center in Beltsville, Maryland and in McMinville, Tennessee. The Arboretum functions as a major center of botanical research conducted by the USDA, including applied research on trees, shrubs, turf, and the development of new ornamental plants. In addition to a library and a historical collection (archive), the institution also has an extensive herbarium of over 800,000 specimens documenting wild and cultivated plant diversity.