In this paper, we examine how the opioid epidemic affected family formation and migration decisions in the United States. Leveraging variation in local exposure to the epidemic—driven by Purdue Pharma’s targeted marketing of OxyContin and proxied by 1996 cancer mortality rates—we find that commuting zones with greater exposure experienced a significant rise in fertility, primarily among unmarried, noncollege- educated women in their late twenties. This increase was accompanied by changes in migration patterns: exposure prompted selective out-migration of college-educated women, who tend to have lower expected fertility early in life. Our findings suggest that the epidemic altered local population composition and contributed to long-term demographic divergence across commuting zones.