Milwaukee County, Wisconsin: History
Portions of what is now Milwaukee County are known to have been inhabited by a number of Native American tribes, including the Sauk, Meskwaki or "Fox", Menomonee, Ojibwe and Potawotami, with elements of other tribes attested as well.
In 1818, when the land later to be Wisconsin was made part of Michigan Territory, territorial governor Lewis Cass created Brown County, which at that time included all the land now part of Milwaukee County. It remained a part of Brown county until 1834, when Milwaukee County was created, including the area south of the line between townships eleven and twelve north (i.e., the northern boundary of Washington and Ozaukee counties), west of Lake Michigan, north of Illinois, and east of the line which now separates Green and Rock counties. This territory encompassed all of what are now Milwaukee, Jefferson, Kenosha, Ozaukee, Racine, Rock, Walworth, Washington, and Waukesha counties, as well as large parts of the present-day Columbia, Dane and Dodge counties.
Milwaukee County remained attached to Brown County for judicial purposes until August 25, 1835, when an act was passed by the Michigan territorial legislature giving it an independent organization. In 1836, the legislature divided the area south and east of the Wisconsin and Fox rivers into counties, as a consequence reducing Milwaukee County's extent to what is now Milwaukee and Waukesha counties. In 1846 Waukesha County was created by taking from Milwaukee all of the territory west of range 21, reducing Milwaukee County to its present boundaries.
The county peaked in its relative importance in Wisconsin in the 1930s–1960s, when about 25% of the state's population resided in Milwaukee County. Its population has been shrinking since 1970.