The Bull Tractor Company of Minneapolis, Minnesota, USA, produced a lightweight prototype, 3 wheeled tractor in 1913. The engine was a twin cylinder 12 hp engined model giving 5 hp at the drawbar. This first model was known as the "Little Bull" and was built for 2 years. In 1915, they introduced a larger model with a 25hp Twin cylinder engine developing 10hp at the draw bar, this was called the "Big Bull". They had a small front wheel with a big rear wheel to keep stable when ploughing. They became one of the biggest suppliers in the 1910s and signed to supply Massey-Harris in Canada, but supply problems meant they couldn't deliver and the deal broke down. The Bull Co. subcontracted manufacture to another firm who then decided to supply other firms, rather than make them under their own name.
Following Fords entry into tractor manufacture in 1917, with their mass production and cheap price of their Model F, which lead to a fall in demand for a lot of small manufacturers as Ford signed large orders with the Governments. Subsequently Bull folded within 3 years.