Originally, the Kinnickinnic River flowed almost directly into Lake Michigan, with water from the Milwaukee and Menomonee rivers flowing south from the center of the city before exiting to the lake. The landform that protected the harbor was a long marshy spit, called Jones Island, that extended southwards from the center of the city. To shorten the distance from the harbor entrance to the city, a "straight cut" was made across the base of the spit, at the northern end. The original harbor entrance was filled in, so that Jones Island was now a peninsula extending northwards, with its base to the south. This effectively lengthened the river, and this new stretch now formed a large portion of the harbor.