The American Museum of Natural History is a natural history museum on Manhattan's Upper West Side, facing Central Park. Chartered by state legislation signed in 1869, it opened to the public in 1871 in Central Park's Arsenal building before moving into its permanent home, which opened in 1877 and has grown into a complex of 45 exhibition halls across 21 interconnected buildings. The museum holds roughly 32 million specimens and artifacts spanning plants, animals, fossils, minerals, and meteorites, maintains a scientific staff of more than 200 researchers, and sponsors more than 120 field expeditions each year. It operates as a private nonprofit and draws about five million visitors annually.