The Cadillac Model Thirty was introduced in December, 1909, and sold through 1911. It was the company's only model for those years and was based on the 1907 Model G.
The engine was the same 226.2 in³ (3.7 L) four cylinder L-head design used in the Model G, and that car's simple sliding-gear transmission was also adopted. The engine was bored out to 255.4 in³ (4.2 L) for 1910 and 286.3 in³ (4.7 L) for 1911 and 1912. The engine was reworked, with a longer stroke, for 1913, giving 365.8 in³ (6.0 L) of displacement.