Cornelius Cornwell constructed a paper mill in the southern part of the city in 1856, beginning a history of paper mills in Ypsilanti that ended with the demolition of the Peninsular Paper Mill around 2004. That first mill was partially destroyed by fire in 1871; another was built in its place, but soon suffered another fire, requiring further rebuilding. By 1888, this mill was joined by the Ypsilanti Paper Company Mill and the Peninsular Paper Mill in Ypsi, as well as the Geddes Pulp Mill and others in Ann Arbor.

After the mill burned for the second time, the Cornwell family donated $1,000 in 1873 to purchase a Third Class Clapp & Jones Steam fire engine for the newly formed Ypsilanti Volunteer Fire Department, which was nicknamed the "Cornwell Company" in honor of the donation.

The Washtenaw County Historical Society discusses the upstream milling activities of several Ann Arbor-based Cornwells, including Harvey Cornwell and sons Henry, Wirt, and "the other one". It is unclear where in that family tree Cornelius fits, though context suggests he is "the other one" of Harvey's sons.

Sources:

In the summer of 1865, a reporter from the Ypsilanti Commercial visited Cornelius Cornwell’s 9-year-old paper mill.