Stulberg first moved to Chicago, where he attended school, worked as a cutter, and joined ILGWU Local 81.
Stulberg moved around the country, working as a cutter and union organizer in Toledo, Ohio, and Chicago (1924–1927).
He also played minor league baseball for the Memphis Chicks, a charter member team of the Southern Association.
In the United States, Stulberg was elected as a vice president and executive council member of the AFL-CIO.
In 1968 he led the union out of the Liberal Party of New York State, which it had helped to found, and he severed the ILGWU's ties to the Americans for Democratic Action.