<P> Mass - production of hardtops began with General Motors, which launched two - door, pillarless hardtops in 1949 as the Buick Roadmaster Riviera, Oldsmobile 98 Holiday, and Cadillac Coupe de Ville . They were purportedly inspired by the wife of a Buick executive who always drove convertibles, but never lowered the top . </P> <P> The Kaiser - Frazer 1949 Virginian was an early example of a four - door hardtop albeit with a removable thin, chrome - and - glass' B' pillar held on by five screws . The car was designed to have a convertible look and padded nylon or cotton was applied over the roof to contribute to the soft - top appearance . </P> <P> Two - door hardtops became popular with consumers in the 1950s while the two - door sedan body fell out of favor among buyers . </P> <P> In 1955, General Motors introduced the first true four - door hardtops . To popularize the introduction of the body style with no B - pillar, GM gave special trim designations for all their brands in North America . The term Seville was used for Cadillac, Riviera was used for Buick, Holiday was used for Oldsmobile, Catalina was used for Pontiac, and Bel Air was used for Chevrolet . </P>

What is the difference between a hardtop and a sedan