Denning manufactured tractors in Cedar Rapids, Iowa in the early part of the twentieth century. Founded as the Estherville Fence Factory in 1893 by J.M. Denning, the company moved to Cedar Rapids in 1899. In 1912 the company sold its fence machinery and patents and became the Denning Motor Implement Company. Denning was purchased by the General Ordnance Company in 1918 and rebranded as National Tractor.