The William T. Bonniwell house is located on Wauwatosa Avenue, approximately one mile due west of a line midway between Thiensville and Cedarburg, Wisconsin. The house sets back from the street on an eminence and looms up majestically.
From a history of Washington and Ozaukee Counties it is learned the first meeting of the county commissioners was held in this structure on November 18, 1840.
The Bonniwsll family are direct descendants of a French Huguenot family by the name of de Bonneville who were driven from France. They were a family of cabinet makers, a craft, which had been handed down from father to son for generations. The first Bonniwell arrived in this country in 1832 and got as far as the city of Montreal, Canada, where he died of the Asiatic cholera. Though the Bonniwell family were not farmers, they nevertheless took up claims for nearly a thousand acres of land in the vicinity of this house.
Before Wisconsin had been admitted to the union as a state Washington and Ozaukee Counties were one. No selection, had yet been.made as which city would be the county seat. The Bonniwell residence was therefore selected for a place for the commissioners to meet and here they transacted the county business until January 1st, 1844. So this was truly the first county seat of those two counties.
The structure is in ruins today. The four walls loom up like a spectre, with tumble-down roof and floors caved in, yet withall the remains have a charm and an interest. As one architect aptly expressed it the building "Outplatts" Charles Platt. It has some most unusual features about it which are found in some of the Italian work of this latter architect. Imagine a building situated even today in a back woods district built along the lines of this house. Where is to be found a house with such an unusual base, stone walls plastered on the outside and scored in a masterly fashion. This scoring seems to be in exact scale with the rest of the building. The window treatments are unusual in that the windows are set way to the front of the wall and are surrounded with a 7" wide outside casing. The whole ensemble is then crowned with a pediment type of classical cornice well proportioned and entirely in keeping with the fine feeling of the rest of the building. The entrance depicts one of the classical type, though the top was restored.
As was stated before the Bonniwells were a family of cabinet makers. The work on the inside of the house certainly shows this. Today after the elements have played their part, much of the woodwork still stands which shows this master hand. For example the treatment around the windows bears the closest study. The jambs of these are all splayed and these together with the heads are paneled. The mantle has an air of refinement to it and the proverbial black walnut staircase (little as there is of it today) shows that much thought and care was lavished on it.