This article examines the patterns of emergence of gay-straight alliances (GSAs) in public high schools in the United States. These extracurricular student groups offer safe spaces, social support, and opportunities for activism to lesbian, gay, bisexual, transgender, queer, and straight students. Combining data on various characteristics of public schools and state anti-discrimination laws with organizational records on the formation of GSA groups, the authors consider the conditions under which these groups are likely to form, as well as the social barriers to their formation. Using logistic regression and linear regression analysis, a number of characteristics common among those schools are isolated that founded the first wave of GSAs. The location of schools, the number of students, region of the country, and support groups outside high schools are among those social forces that promoted the early adoption of GSAs in public schools.