From the City of New York/Parks & Recreation Historical Signs Program:

Washington Square Park is named for George Washington (1732-1799), who served as Commander-in-Chief of the Continental Army during the Revolutionary War and presided over the Constitutional Convention in Philadelphia in 1787. On April 30, 1789, six years after the victory of the colonists, Washington was inaugurated in New York City as the first President of the United States. He served for two four-year terms.

The parkland was once a marsh fed by Minetta Brook. It was located near an Indian village known as Sapokanikan or “Tobacco Field.” In 1797 the Common Council acquired the land for use as a Potter's Field or common burial ground. The field was also used for public executions, giving rise to the tale of the Hangman’s Elm which stands in the northwest corner of the park.

The site was used as the Washington Military Parade Ground in 1826, and became a public park in 1827. Following this designation, a number of wealthy and prominent families, escaping the disease and congestion of downtown Manhattan, moved into the area and built the distinguished Greek Revival mansions that still line the square’s north side. One of these provided the setting for Henry James’ 1880 novel, Washington Square. In 1835, the park also hosted the first public demonstration of the telegraph by Samuel F.B. Morse, a professor at New York University, which is adjacent to the park.

Soon after the creation of the Department of Public Parks in 1870, the square was redesigned and improved by M.A. Kellogg, Engineer-in-Chief, and I.A. Pilat, Chief Landscape Gardener. The marble Washington Arch was built between the years 1890 and 1892 to replace the popular wooden arch erected in 1889 to commemorate the centennial of Washington’s inauguration. The architect Stanford White modeled both structures on the Arc de Triomphe in Paris. Two statues of Washington were installed on the north face of the arch in 1918, Washington as Commander-in-Chief, Accompanied by Fame and Valor by Hermon MacNeil, and Washington as President, Accompanied by Wisdom and Justice by Alexander Stirling Calder.

Other monuments in this park are J.Q.A. Ward’s bust of steel manufacturer Alexander Lyman Holley (1890), Giovanni Turini’s statue of Italian nationalist leader Giuseppe Garibaldi (1888), a World War I flagpole, and the central fountain which was moved here from Fifth Avenue and 59th Street in the mid 1870s.

Use of public space in Washington Square Park has also been redefined throughout the 20th century. Fifth Avenue ran through the arch until 1964 when the park was redesigned and closed to traffic at the insistence of Village residents. With the addition of bocce courts, game tables, and playgrounds, the park has become an internationally known meeting ground for students, local residents, tourists, chess players, and performers. A $900,000 renovation was completed in 1995, and an entirely new renovation is in progress in 2009.