A major United States federal government program to regulate the flow of undocumented workers into the United States-Mexico border region was undertaken in 1954. This program, pushed forward by the Department of Justice (DOJ), was carried out through an Immigration and Naturalization Service (INS) roundup called Operation Wetback, and a DOJ sponsored legislative package titled S. 3660 and S. 3661, popularly known in Congress as the Wetback Bills (Garcia 1980, Langham 1984). Operation Wetback was begun along the California-Arizona border, then moved to the South Texas border, and was finally completed in Chicago. This roundup resulted in an unprecedented expulsion of about 200,000 Mexican undocumented workers, most of them along the international line. During this same period, the Wetback Bills were introduced into Congress. S. 3660 called for sanctions against employers and S. 3661 required seizure of vehicles used to transport undocumented workers. Neither bill was enacted into law. Still the roundup, along with the proposed legislation, signaled dramatic changes in U.S. immigration enforcement policy, especially along the border. The government's enforcement program greatly surprised not only Mexican undocumented workers but also U.S. agricultural employers. Employers in southern and central California, western Arizona and South Texas used large numbers of undocumented workers. They had for a long time depended on undocumented workers to supply cheap labor to plant and harvest crops. The INS targeted these agricultural employers for the roundup. Historically the INS and the employers had enjoyed a tacit gentleman's in which undocumented workers were often allowed to do seasonal agricultural work without worry about apprehension. This off-the-record agreement had worked since the 1920s (Craig 1971, Reisler 1976). In light of this longstanding working agreement, why in 1954 did the government carry out Operation Wetback and propose the Wetback Bills? This article will attempt to answer this question through examination of (1) relationships between government, workers and employers, and immigration, (2) the larger historical context leading up to the enforcement program, and (3) the actual events surrounding it. This article will additionally assess the impact of the government's policy in 1954; examining how it affected Mexican immigration flow up through the adoption of the Immigration and Control Act of 1986. What emerges is a better understanding of why the government embarked on its new policy in 1954, and what it signaled for the future of federal action concerning undocumented immigration across the border.