Before the American settlement of the Chicago area, the lake shoreline fluctuated from year to year as storm waves eroded parts of the shore and built up the shore elsewhere. By 1803, when American troops started the construction of Fort Dearborn, a baymouth bar blocked the mouth of the river causing it to jog southwards and enter Lake Michigan at about the level of present-day Madison Street. When surveyed in 1821 the Lake Michigan shoreline north of the river ran approximately along what is now North Saint Clair Street, just to the east of what is now Michigan Avenue. In 1834, after a number of failed attempts to cut through the sandbar at the mouth of the river, a pier was built to protect a channel cut through the bar. Silt and sand accumulated north of this pier, creating usable land that was later nicknamed "The Sands". Squatters and a vice district encroached on the district, causing angst among the property owners. In 1857, Chicago Mayor John Wentworth evicted these trespassers from the land.