Brewster built the SB2A "Buccaneer" and the F3A-1, which was a licensed F4U.
There were small companies like Hall Aluminum Aircraft Corporation, that built the PH-3 flying boat for the USCG - which was a 1920's design!
And these smaller, often overlooked companies:
Aeronca, Budd, Beechcraft, Cessna, Culver, Fairchild, Fisher, Fleetwings, Goodyear, Howard, Interstate, Naval Aircraft Company, Piper, Pratt-Reid, Ryan, Schweizer, Siskorsky, Stearman, Stinson, Spartan, Taylorcraft, Timm and Waco.