John Deere developed the first American cast steel plow. The implements being used by pioneer farmers of that day were cumbersome and ineffective for cutting and turning the prairie soil. To alleviate the problem, Deere and a partner, Major Leonard Andrus, designed three new plows in 1838. Their cutting part was made from steel cut from an old sawmill blade and shaped by bending it over a log. The moldboard, used for lifting and turning, was made of wrought iron and polished on the upper surface to prevent clogging.
What's it worth? Take a look at this John Deere price guide: sold listings for a value indication.