From 1914 to 1924 the Manhattan Parks Department operated out of the newly built Municipal Building in Lower Manhattan. During this period the Arsenal deteriorated to such an extent that in 1922 a headline in the New York Times read: "Parks Arsenal a Near Ruin." The paper went on to report that this neglected landmark had a leaking roof, broken windows, and missing brickwork among other structural defects.
At that time the City appropriated $75,000 for an overhaul of the Arsenal, including new central turrets and a clock, basement storage for "trees, plant and shrubs," and a conference room for park researchers (later a library). Most of the space was set aside for Parks Department offices. During reconstruction an underground spring and a secret passage were discovered (the latter possibly from the building's days as an arsenal, for the undercover transfer of arms). The restoration was completed in 1924.
Having served off and on as the borough park offices, the Arsenal underwent another complete renovation in 1934 as the first and only headquarters of a citywide unified Parks Department. From his command posts at the Arsenal and at Randall's Island, Commissioner Robert Moses set about directing an unprecedented expansion of the parks system and the modernization of New York City's public facilities. By the time he had left office in 1960, total parks acreage had tripled, and the number of city playgrounds increased from 119 to 777.
In 1935-36 the Arsenal lobby murals were painted under the direction of Allen Saalburg. Saalburg researched images of old New York with particular relevance to city parks, and amplified on his studies in a series of scenes depicting recreational activities, notable park structures, and flagship parks.
The project was funded by the Federal Works Progress Administration. Also at this time, a new entryway was designed for the front of the Arsenal, including military drums over the doorway, and cast-iron musket replicas as supports for the banisters.