Paul Haggis selected Pittsburgh as the main location as he wanted one that was relatively close to the Canadian border, figuring that would be a logical destination for someone breaking their wife out of prison. He also wanted the location to be one less cinematically familiar than New York City or Chicago.
Russell Crowe was Paul Haggis' first choice for the lead. At the time, Crowe was working on Robin Hood (2010), and was tired of the film's lengthy production, so wasn't initially keen about jumping into another film. The script convinced him otherwise.
The "bump key" technique used by Russell Crowe's character does actually work as portrayed on older and cheaper (non-antibump) cylinder locks. However, the car lock tennis ball technique has been busted as a myth on Viewers' Special (2007)
Elizabeth Banks met with prisoners and guards to get a better impression of what life in jail might be like. She was incarcerated in a cell for as long as she could tolerate - which amounted to about five minutes.
Aimee Mann: the Academy Award-nominated musician as an extra in the bar scene when John is looking for Harv. She is seated at the bar with Mike, who joins Harv to meet with John.