The landmark Williams-Steiger Occupational Safety & Health Act of 1970 (OSHAct) guarantees the right to a safe and healthful workplace to large swaths of the American workforce. It replaced a skimpy patchwork of federal regulations primarily governing interstate commerce and covering relatively few workers. In 1970, thousands of workers were killed or succumbed to “recognized” occupational diseases, while other uncounted thousands suffered “unrecognized” occupational diseases. Nineteen states had no workers’ compensation requirements. In states with compensation plans, many workers were ineligible and benefits were meager. Data on rates and types of accidents and injuries were woefully flawed. Workers were kept in ignorance of potential exposures on the job. There were no federal job protections for workers who reported hazardous conditions. The half-century following passage of the OSHAct has seen significant reduction in work-related deaths, injuries, and illnesses. Much of the reduction is partially attributable to OSHA, but some reflects the changing nature of employment and an increased general awareness of environmental hazards. The OSHAct is both a public health and an employment law. It created the Occupational Safety and Health Administration (OSHA) within the Department of Labor (DOL) to administer the law; the National Institute for Occupational Safety and Health (NIOSH), originally in the Department of Health, Education and Welfare, now subsumed within the Centers for Disease Control and Prevention, to provide technical support to OSHA and to actively research new knowledge about occupational safety and health; the independent Occupational Safety and Health Review Commission, with three presidentially appointed members, to decide contested citations or penalties issued by OSHA following inspections; and the National Commission on State Workmen’s Compensation Laws, to study and evaluate the nation’s compensation systems. Here the focus will be on public health aspects of OSHA itself, and a roadmap to its structure, key achievements, and setbacks, as well as to resources produced by salient professional groups that have blossomed as occupational safety and health has matured as a field, will be provided. References on relevant political activism among stakeholders will be included because every aspect of OSHA has been buffeted and constrained by political forces.