This dissertation examines how public private social programs expand to incorporate new groups of citizens over time. I argue that several core features of public private provision, including its requirements for market information and technical expertise, the investment and risks that private providers are often asked to take on, and the state's role in shaping and then backing boundaries to access, give rise to political conflicts between providers, excluded citizens, bureaucrats, and policymakers around issues of access. Examining the development of government homeownership policies and related financial regulations over the twentieth century, I show that groups at the boundaries of inclusion in and exclusion from public private programs - including veterans, African Americans, and women - recognized their exclusion as being generated, in part, by the state and mobilized to redraw the boundaries that had prevented them from accessing homeownership on equal terms as other citizens. In each of these cases, advocacy groups pressed for greater inclusion by appealing to private providers' profit motives, by threatening businesses' position as providers of government-backed benefits, and by contesting the legitimacy of state agencies that sanctioned their members' exclusion. A comparison with the expansion of access to homeownership down the income scale highlights the different political dynamics underlying the expansion of access to groups who are farther from the margins and have a weaker organizational support base from which to draw. Contrary to accounts of the public private welfare state that stress public inattention and business dominance, I show that the public private welfare state can and does generate intense political conflicts between providers, outsiders, and bureaucrats over its terms of access.