Fort Hancock was first garrisoned on March 14, 1898. Sandy Hook had a continual Army population since the activation of the Sandy Hook Proving Ground in 1874, but it was considered a separate unit until 1919, when the proving ground moved to Aberdeen, Maryland and Fort Hancock took over the former proving ground areas. Fort Hancock remained an active Army base until December 31, 1974. The next day, the former base was managed as part of Gateway National Recreation Area, a national park.
The U.S. Life-Saving Service had two stations on the peninsula: the Sandy Hook Station, now the U.S. Coast Guard area; and the Spermaceti Cove Station, which is currently the Sandy Hook Visitor Center. There were also Lighthouse Service and U.S. Weather Bureau employees.
In addition to these federal employees, there were also Western Union and Postal Telegraph Company towers that had employed six men and housed their families.