http://www.britannica.com/EBchecked/topic/220609/John-Froehl...
According to the Encyclopedia Britannica, it was John Froehlich - an Iowa blacksmith - who invented the first gasoline-powered tractor. Apparently a Frenchman (nicolas cugnot) had a steam-powered tractor in 1769, but apparently this was not used for agriculture.
Can't find precisely where he lived, but I imagine that as an Iowan blacksmith he had some experience with the demands and opportunities in farm work.