During the 19th century, the Concord River was near the heart of the US Industrial Revolution. Textile, paper, tanning, and mining industries all emerged during this period. Industrial wastes were dumped into the river, along with untreated sewage and other organic waste. Industrial development within the watershed peaked in the 1920s. The early 1960s saw an increase in the number of chemical and metal firms, many supporting the electronics industry within the Boston metropolitan area. By the 1960s, the Merrimack River was considered one of the top ten most polluted waterways in America. The Concord River empties into the Merrimack River.