The region around the Saginaw Bay and River encompasses the largest contiguous freshwater coastal wetland in America. Because of industrialization and development of population since the 19th century, the Saginaw River and its watershed have been polluted with various wastes discharged into the river and its tributaries. Since the 1970s, federal and state laws have been passed to regulate waste and establish preventive programs. Historically the Dow Chemical Company, with a plant at Midland, Michigan; General Motors, and the cities of Bay City, and the Saginaw have contributed to the release of dioxins into the Saginaw River.