The land making up Ozaukee County was originally part of Milwaukee County which made up the entire southeast section of Wisconsin. In 1830 the first Wisconsin Territorial Legislature set off from Milwaukee County a portion of this land and called it Washington County.

Because of the continued great dissension between several of the communities, principally Port Washington, Cedarburg, Grafton, and West Bend concerning the location of the county seat, the people finally caused the division of Washington County into the two present Ozaukee and Washington counties.