Union Grounds was a baseball park located in the Williamsburg section of Brooklyn, New York. The grounds opened in 1862, its inaugural match being played on May 15. It was the first baseball park enclosed entirely by a fence, thereby allowing proprietor William Cammeyer or his tenant to charge admission. This permitted paying customers to watch the games from benches in a stand while non-paying spectators could only watch from embankments outside the grounds.
"The buildings occupied last winter are left standing, used pretty much for the same purposes as them.[sic] Near these a long wooden shed has been erected, capable of accommodating several hundred persons, and benches provided for the convenience of the fair sex... Several acres more have been added to the enclosure, which is fenced in with a board fence six or seven feet in height.
On the southeast corner a large and commodious club house has been erected, containing accommodations for three clubs. The field is now almost a perfect level, covering at least some six acres of ground, all of which is well drained, rolled, and in a few weeks will be in splendid condition... Several flagstaffs have been put up, from which floated the banners of the clubs o'er shadowed by the nations' ensign."
During its early years Union Grounds was the home field for several ballclubs, notably including the Brooklyn Eckfords, 1862 and 1863 champions of the National Association of Base Ball Players. In 1868, the New York Mutuals moved in from Elysian Fields, Hoboken, New Jersey, long-time home of Manhattan clubs but never enclosed. The ballpark's entrance was on Rutledge Street, and a one-story building in right field, 350 feet away from home plate, was in play.