|Abstract||This dissertation examines the evolution and enforcement of U.S. immigration policy in the twenty years following the passage of the Immigration and Naturalization Act of 1965 (INA), focusing on the U.S.-Mexico border. I argue that immigration policy did not adequately address the reality of the situation along the border. A combination of belligerent rhetoric in the Immigration Service and a profound lack of knowledge on the subject of undocumented immigration made for uninformed opinions and ineffective policies based on unsubstantiated fears of a national crisis, further hindered by poor communication between Washington, D.C. and the border region. Public officials and immigration officers alike faced myriad obstacles to effective border control ranging from budgetary restrictions and internal corruption to fraud and humanitarian crises along the border. Blending political and social history, my research methodology involved analyzing federal records as well as the experiences of people living and working along the border. The disconnect between Washington and the border region explains how the fanfare that surrounded the passage of the INA devolved into frustrations with an unworkable federal policy and inconsistent local implementation. I explore three areas related to the federal-local disconnect that inhibited successful immigration policy and enforcement in the years after 1965: shortcomings in the law, low morale and turbulence in the Immigration Service, and shifting public opinion.