The Immigration Act of 1965 marked a dramatic shift in policy and one with major long term consequences for the volume and composition of immigration to the United States. Here we explore the political economy of a reform that has been overshadowed by the Civil Rights and Great Society programs. We find that public opinion was against expanding immigration, but it was more favorable to abolishing the old country of origin quota system. Votes in the House of Representatives and the Senate were more closely linked to opinion on abolishing the country of origin quotas than to public opinion on the volume of immigration. Support for immigration reform initially followed in the slipstream of civil rights legislation both among members of Congress and their constituents. The final House vote, on a more restrictive version of the bill, was instead more detached from state-level public opinion on civil rights and gained more support from those whose constituents wanted to see immigration decreased.