Photo: Wikimedia Commons. The Columbus Monument at the south west (main) entrance to Central Park at 59th Street and Central Park West (and Broadway), created by Italian sculptor Gaetano Russo and dedicated in 1892. By the 1930s it was severely stained by soot, its base was cracked by vibration, and natural veins in the sculpture itself were opened by vibration and weathering. It was cleaned and restored by the New Deal Monument Restoration Project under Karl Gruppe. And by 2011, when this photo was taken, it was badly in need of another restoration!

References:

1. Maine Monument, New York City Parks website.
2. Parks Monuments Conservation Crew Vintage Film, c.1934 to 1937, NYC Parks Department archive. Video segment 31:37-32:53. “With support from the Federal Works Progress Administration (WPA) this film was taken in the 1930s by Karl Gruppe (1893-1982), chief sculptor of the Monument Restoration Project of the New York City Parks Department, from 1934 to 1937....“
3. New York City Parks Department press release of April 11, 1937: “Mr. Gruppe has been in charge of the monument restoration projects of the Park Department since early 1934 and has superintended the rehabilitation of many of the City's monuments since that time, notable among these projects have been the Maine Memorial and the Columbus Monument at Columbus Circle...”
4. Lowrey, Carol, A Legacy of Art: Paintings and Sculptures by Artist Life Members of the National Arts Club, Hudson Hills (2007): “Gruppe was closely involved in the conservation of New York's public sculptures from 1934 to 1937, during which time, under the auspices of the New York City Department of Parks' Monument Restoration Project and Public Works of Art Project, he chaired a committee of sculptors who oversaw the restoration of significant monuments and fountains throughout the city.”
5. History of New Deal Art Projects: “In 1933 and 1934, during the period of The Great Depression, the Federal government's Public Works of Art Project (PWAP) was organized by the Civil Works Administration. The general purpose of the program was to give work to artists by arranging to have competent representatives of the profession embellish public buildings. This program lasted less than one year, yet it provided employment for approximately 3,700 artists who created nearly 15,000 works of art. In 1935, a similar project, the Federal Art Project (FAP) was established by the Works Progress Administration (WPA). The Federal Art Project continued until 1943...”
6. New Deal Assistance in NYC Parks Department Projects, 1934-43.