The New York times recently ran a map showing where 50,000 guns recovered in violent crime riddled Chicago came from.
"The Chicago Police Department traced the origins of about 50,000 guns that it recovered between 2001 and March 2012. More than half of those guns came from outside the state."
I think it's interesting to note that the states where most of the guns came from are directly bordering it, with the exception of Mississippi. There is a blurb about the MS connection below the map. I would really like to see more about this relationship.
NY Times: Where 50,000 Guns Recovered in Chicago Came From