multiple Central Park civic groups operating under the Parks Conservation Association, were formed in the 1900s and 1910s. These associations advocated against such changes to the park as the construction of a library, sports stadium, a cultural center, and an underground parking lot. A third group, the Central Park Association, was created in 1926. The Central Park Association and the Parks and Playgrounds Association were merged into the Park Association of New York City two years later. The Heckscher Playground—named after philanthropist August Heckscher, who donated the play equipment—opened near its southern end in 1926, and quickly became popular with poor immigrant families. The following year, Mayor Jimmy Walker commissioned landscape designer Hermann W. Merkel to create a plan to improve Central Park. Merkel's plans would combat vandalism and plant destruction, rehabilitate paths, and add eight new playgrounds, at a cost of $1 million. One of the suggested modifications, underground irrigation pipes, were installed soon after Merkel's report was submitted. The other improvements outlined in the report, such as fences to mitigate plant destruction, were postponed due to the Great Depression. 1930s to 1950s: Moses rehabilitation In 1934, Republican Fiorello La Guardia was elected mayor of New York City. He unified the five park-related departments then in existence. Newly appointed city parks commissioner Robert Moses was given the task of cleaning up the park, and he summarily fired many of the Tammany-era staff. At the time, the lawns were filled with weeds and dust patches, while many trees were dying or already dead. Monuments had been vandalized, equipment and walkways were broken, and ironwork was rusted. Moses's biographer Robert Caro later said, "The once beautiful Mall looked like a scene of a wild party the morning after. Benches lay on their backs, their legs jabbing at the sky..." During the following year, the city's parks department replanted lawns and flowers, replaced dead trees and bushes, sandblasted walls, repaired roads and bridges, and restored statues. The park menagerie and Arsenal was transformed into the modern Central Park Zoo, and a rat extermination program was instituted within the zoo. Another dramatic change was Moses' removal of the "Hoover valley" shantytown at the north end of Turtle Pond, which became the Great Lawn. The western part of the Pond at the park's southeast corner became an ice skating rink called Wollman Rink, roads were improved or widened, and twenty-one playgrounds were added. These