The 1951 Chrysler Imperial was the first car fitted with which now common feature?

The Chrysler Imperial, introduced in 1926, was Chrysler's top of the line vehicle for much of its history. Models were produced with the Chrysler name until 1954, and again from 1990 to 1993. The company positioned the cars as a prestige marque to rival Cadillac, Lincoln, Duesenberg, Pierce Arrow, Cord and Packard. According to Antique Automobile, "The adjective ‘imperial’ according to Webster’s Dictionary means sovereign, supreme, superior or of unusual size or excellence. The word imperial thus justly befits Chrysler’s highest priced model."

Three 2-door bodystyles were added to the Imperial model in 1951: a Club coupe, a hardtop and a convertible. Only 650 convertibles were sold and it would be discontinued the following year. 1951 was also the year that Chrysler introduced its 331 cu in (5.4 L) Hemihead V8. "Hydraguide" power steering, an industry first for use in production automobiles, became available on the Imperial for an additional $226. Full-time power steering was standard on the Imperial Crown.