Another report by the private Pew Research Center found a similar decline by looking at the rate of gun homicides, which compares the number of killings to the size of the country's population. It found that the number of gun homicides per 100,000 people fell from 7 in 1993 to 3.6 in 2010, a drop of 49 percent.
Both reports also found the rate of non-fatal crimes involving guns was also down by around 70 percent over that period.
But perhaps because of the intense publicity generated by recent mass shootings such as the December massacre of 20 school children and six educators in Newtown, Conn., the public seems to have largely not noticed the reductions in gun violence, the Pew study shows.
The non-partisan group said a poll it conducted in March showed that 56 percent of people believe the number of gun crimes is higher than it was two decades ago. Only 12 percent said they think the number of gun crimes is lower, while the rest said they think it remained the same or didn't know.
The trend in firearm-related homicides is part of a broad nationwide decline in violent crime over past two decades, including incidents not involving firearms.
But handguns play a major role in violent crime. The Justice study said that in 2011, about 70 percent of all homicides were committed with a firearm, mainly a handgun.
The data was released three weeks after the Senate rejected an effort by gun control supporters to broaden the requirement for federal background checks for more firearms purchases. Senate Democratic leaders have pledged to hold that vote again, and gun control advocates have been raising public pressure on senators who voted "no" in hopes they will change their minds.
Gun rights advocates have argued that people are safer when they are allowed to own and carry guns. Those supporting gun control say that with more background checks, gun violence would drop because more criminals and mentally unstable people would be prevented from getting weapons.