The Chicago shoreline originally consisted of a natural sand edge, with dunes and swales and marshy lowlands. Prior to the 1770s, the area was primarily inhabited by native American Indians. As the shipping industry grew and water-borne travel increased from the Great Lakes to the Mississippi River, via the Chicago, des Plaines, and Illinois Rivers, the importance of the area around the mouth of the Chicago River was quickly realized. To prevent the British and their Indian allies from recapturing this vital water transportation route, Fort Dearborn was built in 1803 on the south bank of the Chicago River.
By the 1830s, urban settlers began arriving. In 1835, piers to protect the harbor entrance and a lighthouse to guide shipping were built. As Chicago grew into a city, which was incorporated in 1833, lakefront shipping expanded. 1848 saw the completion of the Illinois-Michigan Canal. In 1860, the Illinois and Michigan Canal was dredged, and in 1889, the Metropolitan Sanitary District of Greater Chicago was
formed to begin building the Sanitary and Ship Canal. In 1900, the Chicago Sanitary and Ship Canal was completed; as a result, transportation and waste-carrying capacity was greatly increased and the river's flow was reversed inland to the Calumet River.