The Chicago Harbor is located along the southwestern shoreline of Lake Michigan at the mouth of the Chicago River. The breakwater system was first developed as the need to protect ships carrying manufacturing supplies increased dramatically during the the spread of the Industrial Revolution in the mid-1800s. Initial harbor construction began in 1833 with the famous lighthouse, while breakwater construction began in 1889 and continued through 1923. The types of structures used in the breakwater system include: 1) filled timber crib, 2) stone filled timber crib, 3) laid-up, cut stone and 4) concrete caissons (breakwater cross sections). The harbor itself consists of a 970 acre outer basin protected by exterior breakwaters measuring 12,663 ft and a 22 acre inner basin protected by interior breakwaters measuring 6,578 feet.
However, the harbor experienced a severe decline in usage during the1960s. This can be attributed to record low water levels, the completion of the St. Lawrence Seaway in 1959, the expansion of downtown Chicago and the contamination of the Chicago River. Needless to say, the harbor was nearly abandoned. Recently, economic activity has increased near the harbor, mostly thanks to the completion of Navy Pier in 1994.
Today the importance of the Chicago Harbor breakwater system cannot be overlooked. It protects several important structures bordering the lake, more specifically Navy Pier, The James W. Jardine Water Purification Plant, Monroe Harbor and the Chicago Locks. Navy Pier is one of the premier attractions in the City of Chicago, and draws nearly 7 million visitors every year. The water purification plant provides clean drinking water to nearly 2.5 million people (roughly 60% of the total population) in Chicago. Monroe Harbor is one of the largest harbors on Lake Michigan while the Chicago Lock is one of the most used locks in the nation by government, commercial and private vessels.
Link to a physical model of the Chicago Harbor in Plan view.