Since 2015, tens of millions of guns have entered the U.S. market. Using household survey data, we found that the number of firearms owned by U.S. adults increased from 265 million in 2015 to 326 million in 2019. Over this period, the proportion of firearms that were handguns increased slightly, from 42 to 44 percent, continuing a long-standing trend. Seventy percent of handguns were pistols (102 million) and 30 percent revolvers (43 million); 5.7 million were stored in cars. Sixty-three percent of long guns were rifles (113 million); 37 percent were shotguns (65 million). Of the 40 percent of rifles that were semiautomatic, half were described as military-style rifles (23 million) and half as hunting rifles (22 million). Gun ownership was highly concentrated: 87 percent of all firearms were owned by the half of gun owners who owned more than two guns. We discuss the public health and surveillance implications of these findings.