Beginning in the 1870s, America underwent a second industrial revolution driven by the metal industries. For the worker, opportunities abounded; the United States experienced a massive migration from country to city, while immigrant workers flocked to America from Eastern and Southern Europe. As industrial wealth grew, so did class divisions and class unrest. In this period, a succession of organizations sought to mobilize workers according to a variety of ideologies and structures. Labor unions achieved a number of important industrial reforms.The following primary source set contains primary and secondary source documents accompanied by annotations and questions, classroom activities, and relevant standards.