The first articulated four-wheel drive tractor was built by Wagner Tractor of Portland, Oregon. The Wagner brother had been building machinery for logging and mining since 1922. After the 8020 proved unsuccessful, John Deere and Wagner entered a deal for Wagner to build tractors for Deere. At the time, there was still not a large demand for the big tractors, and only 51 were purchased by Deere. Deere re-entered the market with their own tractor (the 7020) in 1971. A five-year no-compete clause in the contract left Wagner unable to built tractors, and ended Wagner in the agricultural market.
Big Tractor Power - site dedicated to high-horsepower four-wheel-drive tractors
WagnerTractors.com - site specific to Wagner and Wagner-built tractors