The company built small steam locomotives early on; the first gasoline-fueled internal combustion engined locomotive was built in 1924 and the first diesel locomotive in 1927, a 30-ton diesel-electric for the Northern Illinois Coal Company of Boonville, Indiana.
An extensive range of diesel locomotives in all industrial sizes followed, utilizing either mechanical torque converter or electric transmission, the former for the smaller locomotives. Most were used by a variety of industrial users, but some railroads also bought Davenport locomotives, particularly of the 44-ton size, that being the largest locomotive then allowed by union rules to be operated by one man. Railroad buyers included the Rock Island, Milwaukee Road, Santa Fe, the Frisco, and the Missouri Pacific. In 1963, that rule was relaxed and railroads ceased buying industrial-sized locomotives for light switching.
Davenport built a number of locomotives for the United States Army during World War II and subsequently eighteen larger switchers during the 1950s, two of which were adjustable in gauge -- one could operate on broad gauges up to 66-inch, and one on narrow gauges -- the latter operating for a period on the Denver & Rio Grande Western.