John Deere (the man) didn't invent the plow. It is as old as antiquity. What he DID discover was that if the moldboard of the plow were made of polished steel, instead of cast iron, the sticky prairie soil would not adhere to it.
It was this initial discovery that led to John Deere's success as a manufacturer of plows and implements.
Read about the life of John Deere
The John Deere Company remained under control of the descendants of John Deere's family for MANY years. You can read about that at JDHeritage.net. When you get there, look for the link that says "Leaders of Deere".