There Can Only Be Estimates
There is no way of knowing the actual number of privately owned guns in the United States. Each state has its own system of counting and classifying guns. Some states do not require registration of guns, and unregistered guns cannot be included in an official count. The result is that there can only be estimates of the total number of guns that American citizens possess.
The ATF Estimates
The Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) is a law enforcement organization in charge of reducing violent crime, among other tasks. One of its duties is to try to keep legally acquired firearms out of the hands of criminals. The ATF is also responsible for estimating the total number of firearms in the United States. It does this by adding domestic firearms production and imports since 1899, then subtracting firearms exports during the same period. In its report Commerce in Firearms in the United States (February 2000), the ATF estimated that about 4.5 million firearms, including approximately two million handguns and about two million second-hand firearms, are sold in the United States each year. The ATF does not take into account guns that are destroyed or that no longer work. The ATF statistics also do not account for guns smuggled into or out of the United States or guns manufactured illegally. As these variables suggest, no one really knows the number of firearms in the United States.
According to the ATF report Firearms Commerce in the United States—2001/2002, during the one-hundred year period from 1899 through 1999, an estimated 248 million guns became available for sale in the United States (not including those produced for the military). This number included more than 87 million rifles, 86 million handguns, and 72 million shotguns. According to estimates from the ATF, there were 1.5 million guns produced in the United States in 1950, 3.7 million in 1970, 5.6 million in 1980, 3.8 million in 1990, and 4 million in 1999. The ATF data suggest that the number of imported rifles, shotguns, and handguns combined averaged one million per year in the 1990s, with handguns accounting for roughly half of that figure. Exports averaged fewer than 400,000 per year. Putting all estimates together, by the end of 1999, the total number of guns privately owned or available for sale in the United States came to more than 260 million, nearly enough for every man, woman, and child in the country to own one.