Organized interests are perennially under fire for distorting public policies. Critics charge that they privilege the demands of favored constituencies at the expense of the broader public interest. Yet despite the importance of interest groups in the political process, little systematic research has been conducted into the development of political identities and lobbying capacities among major advocacy organizations. How does a group come to represent a set of interests? Are the identities and policy priorities of advocacy organizations stable over time, or do they evolve? What causes such evolution to occur, and what tensions arise as a consequence? This book explores the development of interest-group politics in the United States through the defining lens of four key advocacy associations in two major and highly contested policy domains, the small business and environmental lobbies. Through close examination of the National Small Business Association, National Federation of Independent Business, Sierra Club, and National Resources Defense Council, McGee Young addresses questions of how groups come to represent particular interests, which groups succeed and which fail, and how groups shape political institutions. Young explains how political opportunities shape entrepreneurial efforts to form organizations, how formative events shape advocacy strategies and tactics, and how an interest group's identity arises from entrepreneurial "opportunity seekers" interacting with the broader ebb and flow of politics. He shows that received understandings of what constitutes a small business or environmental interest only gradually solidified as policy conflicts forced group leaders to stake out firm principles—such as when pivotal battles in the 1950s over Western dams intersected with a longstanding membership tradition to transform the Sierra Club, or when the NFIB struggled to balance its conservatism with its hostility toward big business, to the dismay of its political allies. Developing Interests bridges the gap between traditional interest-group research and new research in American political development. It marks the first extensive study of small business interest groups in more than 40 years, while its organizational perspective provides a fresh look at environmental politics, and it features the first organizational histories of the NFIB, the NSBA, and the NRDC. With its illuminating case studies of small business lobbies and environmental groups over time, it provides readers with new insights into both the theoretical and empirical significance of interest-group development.