This first of the letter series cars didn't actually bear a letter; it can retroactively be considered the “300A.” The “C-“ designation was applied to all Chrysler models, however for marketing purposes the numerical series skipped more than 225 numbers forward in sequence in order to further reinforce the 300's bhp rating. The 300 originally stood for the 300 hp (220 kW) engine. The C-300 was really a racecar aimed at the NASCAR circuits that was sold for the road for homologation purposes, with Chrysler's most powerful engine, the 331 cu in (5.4 L) FirePower "Hemi" V8, fitted with twin 4-barrel carburetors, a race-profiled camshaft setup, solid valve lifters, stiffer suspension and a performance exhaust system. By 1956 this would be the first American production car to top 355 hp (265 kW), and the letter series was for many years the most powerful car produced in the United States.

The car's "Forward Look" styling can be attributed as much to the Chrysler parts bin as designer Virgil Exner. The front clip, including the grille, was taken from the Imperial of the same year, but the rest of the car did not look like an Imperial. The midsection was from a New Yorker hardtop, with a Windsor rear quarter. Exner also included base-model Chrysler bumpers and removed many exterior elements such as back-up lights, hood ornament, side trim, and exterior mirrors. An electric clock and two-speed windshield wipers were standard. There were few options available including selection of three exterior colors (red, white and black) and only one color of tan leather interior. Power windows and power seat were available but air conditioning was not available in 1955. At least one known 1955 C-300 had A/C as a special order for a Chrysler executive.