A fascinating new history of Texas that emphasizes the importance of Mexico's political culture in attracting US settlers and Texas's unique role in the nation-building efforts of both Mexico and the United States. Why did tens of thousands of Anglo settlers renounce their US citizenship and declare their loyalty to another country by migrating to the Mexican Republic of Texas between 1821 and 1836? In One National Family, Sarah K. M. Rodríguez challenges traditional assumptions about early North American history to draw new conclusions about the comparative power, viability, and nation-building of Mexico and the United States. Drawing from archival research in both countries, Rodríguez highlights a profound political irony at the core of US expansion—that it was spurred by US weakness and Mexican viability. Rodríguez argues that Mexican federalism, long blamed for the country's disintegration and instability, was precisely what attracted thousands of US immigrants to Mexican Texas. Mexico's comparatively weak fiscal structure, ample land, and commitment to dual sovereignty made it an appealing alternative to the thousands of US agrarians who were disillusioned with the United States' political and economic centralization. Yet if Mexico's political system was its strength in the 1820s, it would be the source of conflict and secession by the 1830s. Both Mexico and the United States confronted the limitations of federalism in their respective journeys from loosely confederated republics to consolidated, modern nation-states. But precisely because of its traumatic territorial losses in the mid-nineteenth century, Mexico embraced the characteristics of modern liberal democracy—majoritarianism, territorial sovereignty, and racial equality—far sooner than the United States did. Published in cooperation with the William P. Clements Center for Southwest Studies, Southern Methodist University.