This paper uses textual analysis and plausibly exogenous instruments based on out-of-industry geographic connections and director networks to assess the role of trade associations in forming corporate strategies. Companies are most likely to join trade associations when innovative opportunities have declined, and they are older and larger. Joining associations then induces members to increase profits and markups, improve risk management, find acquisition partners and improve efficiency. To assess mechanisms regarding higher profits, we consider product pricing strategies and high dimensional analysis of market-exclusivity in how firms expand geographically across U.S. states. Overall, we find strong support for the conclusion that associations bring mutually beneficial gains to their members and their industries, and some evidence of an externality in the form of anti-competitive pricing and market-exclusion strategies.