Harry Ferguson started in the tractor business selling Waterloo Boy tractors (renamed Overtime) in Ireland and England during World War I. While working with farmers to maximize the use of their new tractors, Ferguson began working on a better system to attach implements. His "Ferguson System", later known as the three-point hitch, would become the standard for attaching implements to farm tractors.
To demonstrate his new hitch, Ferguson built the Ferguson Black tractor. This led to an agreement with David Brown to build the Ferguson-Brown. The arrangement was short lived, and Ferguson made a new deal with Henry Ford to develop tractors using his hitch. The deal with Ford lasted until 1947, when it ended with a bitter lawsuit. Following this, Ferguson entered into an arrangement with the Standard Motor Company to produce his own line of tractors. Ferguson was taken over by Massey-Harris in 1953. The Massey-Ferguson brand is still used today by AGCO.
AGCO Massey-Ferguson - official site
Old Ferguson Tractors - wide range of resources on Ferguson
Storment Family Ferguson Tractors - a family's collection
Ferguson Enthusiasts - Ferguson club in North America