Below Replacement, Unequally: Settlement-Era Regional Cultures and U.S. County Fertility

The United States total fertility rate reached a record low of 1.60 in 2024, but the national figure conceals durable regional variation. This article maps contemporary fertility onto the American Nations model, a typology of settlement-era regional cultures (Woodard 2011) that follows county borders and has been applied to violence, health, and political outcomes, but not to fertility. Using CDC WONDER natality data (2021-2024 pooled), Census Bureau denominators, and a tract-level cultural-region crosswalk published by the Urban Institute, total fertility rates are computed for each nation and county-level models estimated with controls for religious adherence, income, education, and urbanicity. Nation-level TFRs range from 1.42 on the Left Coast and 1.54 in Yankeedom to 1.73 in Greater Appalachia and 1.77 in New France; every region is below replacement. Cultural region adds 11 percentage points of explained variance in county TFR beyond the controls, and the regional ordering echoes the geography of the antebellum fertility decline, in which Yankee-settled areas led the nation. Settlement-era cultural boundaries remain a live axis of American demographic variation two centuries later. Includes the full analysis pipeline and derived datasets.