What was the first American automobile to be equipped with a V8 engine?

In 1907 The Hewitt Motor Company built a large 5 passenger Touring Car. It was equipped with a hefty V8 engine that developed 50/60 horsepower and had a bore of 4 inches and a stroke of 4 1/2 inches. The Hewitt was the first American Automobile to be equipped with a V8 engine.

De Dion-Bouton introduced a 7,773 cc (474 cu in) automobile V8 in 1910 and displayed it in New York in 1912. It was produced only in small quantities, but inspired a number of manufacturers to follow suit.

One of the first production automobile V8s was introduced in the United States in 1914 by Cadillac, a division of General Motors which sold 13,000 of the 5.4 L (330 cu in) L-head engines in its first year of production. Cadillac has been primarily a V8 company ever since. Oldsmobile, another division of General Motors, introduced its own 4 L (244 cu in) V8 engine in 1916.