This document lists 20 concept cars from the 1950s and 1960s that were designed by major American automobile manufacturers like Chrysler, Buick, Ford, GM, Lincoln, Oldsmobile, Cadillac, De Soto, Packard, and Pontiac but were never put into production. Ranging from 1951 to 1959, the concepts showcase innovative designs that explored new automotive styles and technologies ahead of their time.