Who was the pioneer who planted apple trees?

Probably John Chapman, though he didn't actually plant the trees; he sold the saplings for other people to plant. He got the nickname "Appleseed" because he started his business with seeds he collected from Apple MASH. In his day, Apples weren't so much for eating as for making cider, and from it, Applejack, a liquor. Today we have varieties grown for tastiness, but in Chapman's time, most Apples were too bitter to munch on. His trees, however, improved somewhat on that condition.