The Firmenich family should be listed somewhere in the 1850 US Census since they arrived in 1847 and then were mentioned living in the Milwaukee, Wisconsin area. It is possible they were missed, but it is more likely that their surname was transcribed incorrectly or I am looking in the wrong place. Mathias’ obituary stated that they lived 25 miles from Milwaukee, which is probably located in the northern Milwaukee County area or southern Washington County (now also Ozaukee County) area.
I’ve personally browsed line-by-line through most of the general area and have not yet found anything similar to “FIRMENICH.” This includes all of Granville in Milwaukee County, Mequon & Germantown in Washington County, and Menomonee [Falls] in Waukesha County. These are all in that general area. His future wife, Pauline Thompson, and her family lived in the Granville area, also. I will need to check further in on my next pass-through.