In the 1930s, social workers employed by New Deal agencies in Puerto Rico played central roles in advocating for the coverage of Puerto Rico under new federal social welfare provisions. These social workers fought for the island to be included under the Social Security Act of 1935 by building political coalitions to petition the US Congress for inclusion. Territorial law allowed the US Congress to determine on a case-by-case basis how to administer federal policies, including social welfare provisions, which they restricted based on popular colonial discourses that cast Puerto Ricans as racially inferior and that justified US imperialism. This essay explores how social workers organized and were successful in achieving the partial coverage of Puerto Rico under amendments made to the Social Security Act in 1939. However, these changes were slow, and while further coverage was expanded over the proceeding half century, the island still remains only partially included under federal policies that are still determined by the US Congress.