The Impala began life in 1958 as a dressed-up Bel Air rather than a car in its own right: longer wheelbase, a shorter greenhouse, brushed-aluminium trim, but no separate “Bel Air” badging to distinguish it in showroom literature.[1] It rode on a new X-frame chassis GM claimed was more torsionally rigid than the perimeter frame it replaced, though the design proved worse in side-impact protection than the construction it superseded, a trade Chevrolet made for two model years before moving on.
This entry covers only the 1958 model year, GM’s 50th-anniversary year, in which the Impala was built solely as a two-door hardtop or convertible; the four-door and wagon body styles that came to define later Impalas did not arrive until the redesigned second generation for 1959.