Illegality | Illegal entry into the United States is overwhelmingly a post-1965 and Mexican phenomenon. For almost a century after the adoption of the . Constitution, no national laws restricted or prohibited immigration, and only a few states imposed modest limits. During the following 90 years, illegal immigration was minimal and easily controlled. The 1965 immigration law, the increased availability of transportation, and the intensified forces promoting Mexican emigration drastically changed this situation. Apprehensions by the . Border Patrol rose from million in the 1960s to million in the 1970s, million in the 1980s, and million in the 1990s. Estimates of the Mexicans who successfully enter illegally each year range from 105,000 (according to a binational Mexican-American commission) to 350,000 during the 1990s (according to the . Immigration and Naturalization Service).