Wikipedia says that the the Lapeer County Courthouse is the oldest original courthouse structure still in use in the state of Michigan, and one of the ten oldest in the nation.
The City of Lapeer’s history page adds:
Folklore claims Lapeer was derived from the naming of the south branch of the Flint River, which flows northwestward over quite a long distance of rocky bed in Lapeer County. French and Indian traders frequently passed over this section of the county and through the river, ultimately naming our city for the stone that lay at the river bottom. The translation of stone in French is “LePierre”; the English translation of Canadian French accent of this word is “Lapeer”. The river was named Flint, synonymous with stone.
Lapeer County was once part of the Northwest Territory. By an ordinance of the Congress of the United States passed July 13th, 1787, the whole of the territory of the United States lying northwest of the Ohio River, though still occupied by the British, was organized as the Northwest Territory. In January of 1820 the County of Oakland was formed. Governor Lewis Cass set Lapeer County’s boundaries on September 18th, 1822, although it remained part of Oakland County until it was organized. Lapeer County officially became a county on February 2nd, 1835.