Tom Petty mentioned back in 1982 while filming the video for his song "You Got Lucky" (a post-apocalyptic themed story) he wanted to do a small part in a futuristic movie. He said he wanted to portray a post war character, which he finally did in this movie.
The actors did their own stuntwork on the rope bridge scene and Kevin Costner, a skilled equestrian, did his own horse-riding. He also performed the cable cart scene himself, with the cart winched through the air by helicopter.
On his personal website, author David Brin reveals that while studios were bidding for the book, his wife decided during a screening of Field of Dreams (1989) that Kevin Costner should portray The Postman. Brin agreed that the emotions evoked by that film matched the message he intended to deliver with his novel. A decade later, after learning Costner would be cast as the lead, Brin said he was "thrilled."