Factual error: Joe Jackson batted left-handed in real life, not right-handed as Ray Liotta portrayed. He also threw right-handed and not left-handed like it shows when Kevin Costner is hitting him fly balls to left field.
Factual error: When Ray is walking around the Chisholm Minn, he wipes the dirt off a license plate to reveal a sticker showing the year '72. While Minnesota began using stickers in 1972, they only started putting them in the lower right starting in 1975, with all plates before 1975 containing an embossed year in the lower right.
Factual error: When Ray is in the feed store, he picks up a bag of seeds from the counter and casually walks out. These bags of seeds weigh 50 pounds, so to lift it in the manner he did would require a great deal of strength.
Factual error: Philadelphia Athletics players are wearing green. They didn't wear green until 1963. They wore blue prior to that, very similar to Dodger blue.
Factual error: The catcher appears with the other players when they come out of the corn. The catcher was never included in the scandal, nor was a catcher banned.
Answer: It was actually his own voice (Kevin Costner) that sent him on the journey. At the end of the movie there's even the part where Ray is recalling the voices he heard and turned to Shoeless Joe Jackson and says, "It was you". At which point Joe Jackson turns around and says, "No Ray. It was you".