Central Park initially opened in 1857, on 770 acres (3.1 km2) of city-owned land. In 1858, Frederick Law Olmsted and Calvert Vaux won a design competition to improve and expand the park with a plan they entitled the Greensward Plan. Construction began the same year and was completed in 1873. Central Park has been a National Historic Landmark since 1963. The park, which receives approximately twenty-five million visitors annually, is the most visited urban park in the United States. It is 2.5 miles (4 km) long between 59th Street (Central Park South) and 110th Street (Central Park North), and is 0.5 miles (0.8 km) wide between Fifth Avenue and Central Park West.