In 1893, Frederick Jackson Turner argued that the American frontier fostered individualism. We investigate the Frontier Thesis and identify its long-run implications for culture and politics. We track the frontier throughout the 1790–1890 period and construct a county-level measure of total frontier experience (TFE). Historically, frontier locations had distinctive demographics and greater individualism. Many decades after the closing of the frontier, counties with greater TFE exhibit more pervasive individualism and opposition to redistribution. Suggestive evidence on the roots of rugged individualism points to selective migration, the adaptive advantage of self-reliance, and opportunities for upward mobility through effort.