Despite a deep concern from policymakers and the public alike, detailed records linking military service records and suicide do not exist on a national scale. Here, we determine how suicide rates are related to the veteran population by linking data from the Centers for Disease Control (CDC) at the county-level with estimates of veteran populations by service period from the American Community Survey. While this is an indirect approach, this panel analysis allows us to uncover a robust and persistent finding: counties with larger Vietnam veteran populations have higher suicide rates. Our modeling strategy includes standard panel data methodology, sub-state analysis based on the adoption of Child Access Prevention laws governing firearms, and a recent innovation in instrumental variables methodology coupled with county birth records from lottery years as an instrument. Ultimately, we find that a standard deviation increase in the Vietnam veteran population is associated with 1.9 to 6 additional suicides per 100,000 people.