During the First World War, Howell worked as a seaman and served as part of a Jamaican contingent sent to Panama. Before temporarily settling in Panama in 1918, he travelled back and forth between New York City and Panama several times. While in New York he became a member of Marcus Garvey’s Universal Negro Improvement Association (UNIA) after being confronted with his identity as a black man in Harlem for the first time and meeting Garvey, the revolutionary UNIA leader, in person.