We provide the first national analysis of mortality in the U.S. homeless population by linking 140,000 homeless individuals from the 2010 Census to twelve years of all-cause mortality data from the Social Security Administration (SSA). Non-elderly homeless individuals face 3.5 times the mortality risk of the housed after accounting for demographic differences and geography, with a time pattern suggesting that persistently poor health, rather than homelessness itself, primarily drives this disparity. Employment, higher income, and more extensive recent family connections are associated with lower mortality, underscoring the persistence of health disparities into the extreme lower tail of socioeconomic disadvantage.