Character mistake: Red says that Andy crawled to freedom through 500 yards - 'just shy of half a mile'. 500 yards is far less than half a mile; in fact, it's less than a third of a mile. It is however just shy of half a kilometer, which may be what King was thinking of when he wrote the book.
The Shawshank Redemption (1994)
1 character mistake - chronological order
Directed by: Frank Darabont
Starring: Morgan Freeman, Clancy Brown, Tim Robbins, William Sadler, Bob Gunton, Gil Bellows
Factual error: When Red is sitting under the oak tree in 1967 and pulls the money out of the envelope, the top bill is signed by Nicholas F. Brady, who was Secretary of the Treasury September 1988 - January 1993. It's less about reading the handwriting as noting the different appearance of different signatures from different eras. (02:14:40)
Andy Dufresne: Get busy living, or get busy dying.
Trivia: There are many references to the number 237 in the movie. For instance, this is the number of Red's cell, and these digits are on Andy's prison I.D. This number makes appearances throughout Steven King stories, the most famous one being the room where the murders take place in "The Shining".
Chosen answer: In a nutshell, tax evasion. He's running the prison like a company doing building work with, as its described by the builder in the movie, a pool of slave labour to allow him undercut other contractors. He is skimming profit for his own pockets, along with taking bribes, etc. that Andy's creative book keeping is hiding from the IRS.