The party proclaimed itself on 7 July 1933 at 1032 Prospect Avenue, Bronx, Branch headquarters of its predecessor Industrial Union League (IUL).

The new IUP immediately announced candidates in the New York City elections: Adolph Silver for Mayor, Irving Oring for Comptroller, and Sam Brandon for President of Alderman.

Yet the immediate roots of the Industrial Union League were in the SLP's mass expulsion of Section Bronx during the 1920s.

[2] In November 1933 a furniture union in Jamestown, New York, the United Workers of America, was founded on industrial unionist principles compatible with the views of the IUP.

[3] The union affiliated with the Bronx-based party in December of that year, and soon formed a "mixed trades" local in Erie, Pennsylvania.