The Diamond T Motor Car Company manufactured automobiles until 1911 when the first truck led to exclusive truck production and soon gained legendary status as style leaders. While "The Handsomest Truck in America" became a long-standing slogan, Diamond T also emphasized its engineering leadership. Builders of more than 1500 Class B "Liberty" trucks in World War I, Diamond T produced nearly 50,000 thousand prime movers, half-tracks, army wreckers, tank tractors, and tank movers in World War II. The late 1940s were years of peak production, but as the 1950s progressed, Diamond T found independent status problematic.

The White Motor Company purchased Diamond T in 1958; moving production from Chicago to Reos manufacturing facilities in Lansing, Michigan, in 1960, creating the Lansing Division to produce Diamond T and Reo trucks. Both Diamond T and Reo ceased to be separate trucks starting in 1967 when Whites new Diamond Reo Division began producing Diamond Reo trucks.