Make a historically-specific, arguable claim about the negative impact of undocumented immigration. First, you need to ground yourself historically (and accurately): no person entered as an undocumented immigrant until after 1882 with the Chinese Exclusion Act, and the vast majority of immigrants faced no restrictions until the 1924 National Origins Act. Confine the time frame of your paper to the period after 1882, and perhaps even after 1924; remember, too, that you must end your paper in 1980 as required by the assignment.To shape your thesis into a coherent argument, you need to go back to the beginning ask yourself what is the analytical question or problem of your paper. What key question about the history of illegal immigration are you seeking to answer? What historical problem do you want to explore? One important strategy for you to use to define that question is to take a closer look at your evidence. Review your evidence closely and try to understand what is interesting, contradictory, or challenging about it. And here you must look closely at the evidence that you do have and what it says about the period you are discussing and make sure you draw conclusions that the evidence supports. That will likely point you toward the central question you want to answer and help you state a clear arguable thesis.