A plow is a farming implement used to loosen the soil and create furrows prior to planting seed. Possibly the deepest that soil was penetrated during the horse drawn years was by this type of tool.  John Deere is given credit for coming up with the idea of a curved mold board made of steel with a removable shank.  A plow this size probably used six horses.

Three bottom plows at the Heritage Center

Read the Wikipedia article for more information on plows.

1995.056.001, Three bottom plow