A central insight in economic sociology is that firms depend on relationships with other organizations for their access to capital, information, and other resources. Such interactions among firms tend to develop into stable networks of social and economic exchange that stratify fines in an industry. My dissertation contributes to our understanding of emergent industry structures by explaining how firms build their networks during the early history of a new sector. First, I propose that firms in young industries are exposed to multiple institutional pressures from professional groups, policy makers, neighboring industries, and trade associations. Second, I argue that institutional pressures shape firms’ collaborative strategies. Finally, I claim that firms are not uniformly affected by institutional pressures, since they typically differ in their exposure to different collaborative practices and beliefs. I find empirical support for these claims in a multi-method study of the U.S. venture capital industry during its formative years 19651988. The empirical results highlight that a young industry can develop along many different trajectories. Understanding how firms historically were affected by different institutional pressures is crucial for explaining contemporary industry structures and business practices.