We document how childcare costs and the location of extended family influence the labor supply and mobility of US women. Women return to their home locations immediately before fertility events, suggesting that informal childcare needs may motivate home migration. Women who live near their parents have lower child earnings penalties. We then build a model of labor supply and migration to assess the impacts of childcare subsidies. Childcare subsidies increase earnings and mobility among US women and ignoring migration can understate the welfare benefits of these policies, especially for college‐educated women and those whose parents' locations have poor amenities.