The American politics literature on representation focuses on voters and elected officials, but a growing group of political scientists is arguing that more should be done to study interest groups. Yet there already is a large literature on interest groups-and it has struggled to show evidence of interest group influence. I argue here that the interest group literature's nearexclusive focus on the federal government has hindered its progress: basic questions have gone unasked, important interest groups have gone underappreciated, and the amount of influence has been underestimated. By studying U.S. subnational policymaking, scholars would discover different constellations of interest groups, and they would find that the variation in subnational governments allows for empirical designs that are better able to detect interest group influence when it exists. The payoffs of a subnational focus would be substantial-both for our understanding of interest groups and for the study of political representation.