Following the United States' entry into World War I in April 1917, Palmer volunteered, despite his Quaker background, to "carry a gun as a private" if necessary, or to "work in any capacity without compensation." He chaired his local draft board for a time, while Herbert Hoover, head of the new Food Administration refused to appoint him to a post in his agency. In October, he accepted an appointment from Wilson as Alien Property Custodian an office he held from October 22, 1917, until March 4, 1919. A wartime agency, the Custodian had responsibility for the seizure, administration, and sometimes the sale of enemy property in the United States. Palmer's background in law and banking qualified him for the position, along with his party loyalty and intimate knowledge of political patronage.