The Capitol Grounds a.k.a. Capitol Park (I), was a baseball field in Washington, D.C. The grounds were the home field for the Washington Nationals of the Union Association during the league's only season in 1884. The ballpark had a seating capacity of 6,000, and was where the Russell Senate Office Building stands today. The ball field was bounded by C Street NE (north); Delaware Avenue NE (west): B Street (now Constitution Avenue) NE (south); and First Street NE (east); just northeast of the Capitol building.