By the late 1930s the voiturette class had become highly competitive, driven by the introduction of the Alfa Romeo 158 and the ERA B- and C-type models. This forced Maserati to design an entirely new engine: a square-bore inline-four cylinder unit with a bore and stroke of 78 mm giving a total displacement of 1,490.85 cc. The engine produced 30 to 50 bhp more than the previous inline-six it replaced, achieved primarily through a four-valve-per-cylinder head configuration combined with a more powerful supercharger and a slight increase in compression ratio.
The engine followed customary Maserati practice in being mounted into a chassis closely resembling that of the 4CL's predecessor, the Maserati 6CM. The chassis used twin box-section spars joined by ladder-fashion cross-members, with more aluminium componentry than the earlier car. The 4CL's track was 5 cm wider than the 6CM's and it sat lower, thanks to repositioned spring hangers. The body was a low, curvaceous alloy-panel design built in-house; Maserati also produced a streamlined variant from the outset.
The 4CL's race debut came at the 1939 Tripoli Grand Prix, where Luigi Villoresi put the streamlined version on pole position ahead of Mercedes-Benz's new W165s. The result was disappointing: both the streamliner and two of three conventional 4CLs retired early with engine trouble, handing victory to the Silver Arrows. The 4CL's first victory instead came through privateer Johnnie Wakefield at the Naples Grand Prix shortly after. Wakefield took two further wins through the remainder of the 1939 voiturette season; the works cars added another two victories before the outbreak of war ended international competition.
Villoresi drove the 4CL to victory at the 1940 Targa Florio, though the restricted field — limited to Axis countries with only Maserati entering a factory team — limited the significance of the result.
On the resumption of competition in 1946 the 4CL proved the class of the field. Villoresi won the very first post-war race, the 1946 Nice Grand Prix. Tazio Nuvolari and Giorgio Pelassa also took wins, but Raymond Sommer was the outstanding 4CL driver of that season. The 1947 season was the 4CL's most successful: despite Alfa Romeo returning with the revamped 158 and new 308, Maserati drivers claimed 10 individual race victories.
Engine development in response to Alfa Romeo's introduction of two-stage supercharging began to expose the limitations of the existing chassis, and experiments with tubular-section chassis members through 1947 eventually led to the introduction of the revised 4CLT model in 1948.
As the factory switched to the 4CLT, many 4CL chassis passed into privateer hands. The car's popularity among independent entrants meant that 4CLs continued to appear in top-level competition — including at the outset of the Formula One World Championship in 1950 — long after the factory had moved on. The 4CL's accessibility and competitiveness made it the car most responsible for keeping independent racers on the grid during the chaotic transition from pre-war to post-war motor racing.
Numerous 4CL and 4CLT models survive into the present day, regularly appearing in historic motorsport events and museum collections.