Although Cadillac had been building four-cylinder cars since 1905, the single-cylinder line was not abandoned until 1909.

That year, the four-cylinder car was made the sole offering and given a new nomenclature, Model 30, for its horsepower rating.

A refinement of the 1907–1908 Model G, it had a longer wheelbase but was offered only in open body styles.

Selling for about two-thirds the price of the G, the new Model 30 sold nearly six times as many cars as all 1908 Cadillacs combined.

Three body styles were offered: a Roadster, a Tourer, and a Demi-Tonneau.

The latter had a detachable tonneau and could be converted to a runabout.

The Roadster and Demi-Tonneau had a sweeping cowl that presaged “torpedo” styling.

When a windshield was ordered, it was affixed to a wood dashboard fitted over the cowl.

In 1910, closed bodies, a Coupe and a Limousine, returned to the Cadillac line, and by the time that the Model 30 was replaced by the Type 51 V-8 in September 1914, nearly 67,000 had b...