The coal industry exercises a pervasive influence upon mining communities in Appalachia even though it makes minimal contributions to employment. Miners rarely participate in movements that fight against coal companies for better working conditions. One explanation for this paradox is the depletion of social capital. In this article, I first use the existing body of literature to build a theoretical framework for discussing bonding social capital. Second, I analyze how the United Mine Workers of America in Harlan County, Kentucky at the beginning of the twentieth century worked to generate social capital. The results show that these coalfield residents demonstrated a high degree of social capital in terms of a strong shared sense of reliability and a dedication to collective activities and intimate networks. The union during that period engaged in strategies that were instrumental in creating this high level of social capital: holding regular meetings, organizing collective actions, promoting collective identity, and electing charismatic leaders.