Gun violence in New Jersey's cities sent the state's homicide rate to a seven-year high in 2013. Meanwhile, Gov. Chris Christie signed more than a dozen gun control measures into law, driven not only by violence at home but also by a larger national debate over firearms.

Yet like many places in the northeast, most of the guns involved in crimes here in Jersey come from out of state. So exactly where do New Jersey criminals get their weapons?

The interactive map below is based on data released last year by the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, which successfully traced 2,112 of the 3,595 "crime guns" recovered in New Jersey in 2012 (2013 data isn't available yet). The ATF data offers the best available window into the hidden flow of firearms between states. Here are some highlights from NJ.com's analysis:

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• The majority of weapons recovered came from New Jersey's cities: Newark, Camden, Jersey City, Paterson, Trenton, Atlantic City, Elizabeth, Vineland, Irvington and East Orange comprised the top 10 and accounting for 1,959 guns. Another 341 cities and towns accounted for 1,636 guns, but the ATF declined to release town-by-town statistics.

• While new legislation has tried to rein in magazine capacity or restrict access to high-powered rifles, the majority of crime guns recovered in 2012 were handguns. Pistols and revolvers made up a combined 2,903 of the total guns recovered.

• The largest single source for crime guns in the Garden State was New Jersey itself, which accounted for 425 guns. But that's only one-fifth of all the guns traced back to their sources, meaning that New Jersey is a net importer of crime guns. Jersey sent 196 traceable weapons out of state, mostly to Pennsylvania, New York and Florida.

• The majority of out-of-state crime guns came from Pennsylvania and five southern states known for their loose requirements for gun purchasing: North Carolina, Virginia, Georgia, South Carolina and Florida, which accounted for 1,084 guns. Those states represent tributaries of what law enforcement officials call the "iron pipeline," through which guns flow up Interstate 95 and into New Jersey, New York and other states where buying firearms is more difficult.

• The 2012 data shows a pattern that authorities say has been well established. "I've been here a while, and that chart has not really been changing," said Michael Mohr, a special agent in the ATF's Newark Field Division. "That flow of guns from the I-95 corridor really hasn't changed."

Gun control advocates, most notably Mayors Against Illegal Guns, have long pointed to the fact that criminals in states where gun purchases are heavily regulated get most of their firearms from elsewhere as evidence that state-level gun control laws are working, and that a federal law is needed to reign in trafficking. They claim that the ease with which guns can be bought in other states and illegally transported across the border hinders attempts at gun control in states like New York and New Jersey, which grapple with gun violence even as they maintain some of the toughest gun laws in the country.

But gun rights groups contend that criminals willing to violate multiple local and state statutes will get weapons wherever they can get them, and additional restrictions will only keep guns out of the hands of law-abiding citizens.

"What difference does it make where they got them?" said Frank Fiamingo, president of the New Jersey Second Amendment Society. "They'll get them, whether they buy them legally or illegally. Now they can print the damn things. It's not the instrument. It's the use to which the instrument is put."

Fiamingo said curbing the kind of violence that drove up New Jersey's homicide rate last year means focusing on the gangs that fuel the violence, not just the weapons they use.

"Who are they being used by?" he said. "That's the more relevant question."

Since 2008, a state Attorney General's directive has required police in New Jersey to report their trace requests electronically to the ATF and the State Police, who use the data to analyze trends and identify potential gun trafficking rings through a program called NJ Trace.

That more robust reporting means authorities can identify trafficking trends, according to State Police Lt. Stephen Jones.

"We can glean from that where crime guns are being recovered, times of day, what crimes they are associated with," Jones told NJ.com. "That tells you a better way to proactively place your assets in order to combat crime."

The increased scrutiny has collared some sophisticated distribution networks that brought illegal guns from out of state into New Jersey's cities.

Take the case of a drug dealer named Clovis Reeves, who offered bounties of $50 per weapon to Georgia residents with clean records to purchase the guns for Reeves to sell on the streets of Newark. He was sentenced to 12 years in 2008.

Or Trayle Beasley, the first person to plead guilty to the crime of leading a firearms trafficking network in New Jersey. According to Lt. Eric Barlow, a State Police officer who investigated the case, a gun used in the 2009 shooting of a 13-year-old girl in Trenton was traced to the Eastern Shore of Virginia. Investigators started looking at other crime guns recovered in Trenton over several years that could be traced back to that same area, eventually identifying somewhere around a hundred. In 2011, Beasley admitted trafficking at least 50 guns.

These successes have come with some costs, according to police.

"People have caught on that ATF is looking at straw purchases," Mohr said. Word has gotten out that buying a bunch of guns in one state and quickly selling them here will raise red flags. Now, he says, the challenge for investigators is ferreting out illegitimate purchases happening on smaller scales.

"The days of somebody going in and buying 20 9-millimeter [handguns] are over," he said. "The large-scale purchase at one time, we're not seeing that."

There is conflicting data on how big a role organized trafficking plays in putting guns in the hands of criminals, versus other sources, like theft. It's also difficult to get a bigger picture from ATF data in part because federal law restricts what information it can maintain and further restricts what it can release to the public.

The ATF declined requests to provide a more detailed geographic breakdown of the recovery and source sites of crime guns in its 2013 report.