The Duesenberg Model A was the first production automobile with four-wheel hydraulic brakes, introduced in 1921.
Duesenberg's Model A used hydraulic pressure to operate brakes at all four wheels. This was a major technical step because hydraulic systems could distribute braking force more consistently than mechanical linkages. The car also used an overhead-camshaft straight-eight engine, unusual sophistication for its period.
The Model A was produced by the Duesenberg brothers' company before E. L. Cord acquired Duesenberg in 1926. Its engineering reputation helped establish the marque as a maker of technically advanced and high-performance automobiles.
A common mix-up is to credit Chrysler's 1924 Chrysler Six, which helped popularize hydraulic brakes in the mass market. The Chrysler was important, but Duesenberg's Model A preceded it as a production car with four-wheel hydraulic braking.