Throughout most of the nineteenth century, American popular sports developed on the margins of “respectable” society, among groups of men who found greater satisfaction in the dramatic and combative masculinity of sports than in the drudgery of daily life. This sporting fraternity adapted and promoted traditional pastimes, most notably prizefighting, in ways that made them more engaging and also more profitable. The oppositional culture that resulted celebrated toughness, daring, and physical prowess, offered an escape from the stresses of an impersonal, industrializing economy, and provided a symbolic arena for ethnic conflict, especially between native-born Anglo-Saxons and immigrant Irishmen. By the end of the century, as the anxieties of industrialization and immigration spurred middle- and upper-class men to value physical prowess, and changes to prizefighting rules brought the sport greater respectability, it became a national obsession. The rise of college-educated champion James “Gentleman Jim” Corbett, who defeated the freewheeling John L. Sullivan to win the heavyweight championship in 1892, reflected the sport’s transition from its folk, countercultural origins to a form of mass, commercial entertainment.