There are 3 Northwestern PORTERFIELD CP-65 aircraft on the U.S. registry that TailWiki has a page for. Every one is built from the public FAA record — year, serial, engine, home base, and registration history — and owners and pilots add photos, trips, and stories on top. The ones listed here were built between 1940 and 1941.
N37895
1941 Northwestern PORTERFIELD CP-65
Upland, CA
N27254
1940 Northwestern PORTERFIELD CP-65
Tuckerman, AR
N27259
1940 Northwestern PORTERFIELD CP-65
Lockbourne, OH