April 15, 1837
The first boards were sawed by the mill begun by Blodgett and completed with Goodhue.
The propertyGrade A · 1 independent source
The evidence
“Goodhue who, although a native of Massachusetts, had come here with his family from Canada, he in turn selling half his purchase to some other newcomers, John Doolittle and Charles Johnson. After this sale to Goodhue the saw mill, then being built, was completed by Blodgett and Goodhue working together ; in the spring of 1837 water was turned into the mill race and the first boards were sawed April 15.”
1908-brown-rock-county/06-history-of-beloit.md, Vol. 1, PDF p. 147 / book p. 132
Brown, William Fiske, editor. Rock County, Wisconsin: A New History of Its Cities, Villages, Towns, Citizens and Varied Interests, from the Earliest Times, Up to Date. Chicago: C. F. Cooper & Co., 1908. 2 vols. archive.org/details/rockcountywiscon01brow, archive.org/details/rockcountywiscon02brow.
Grade A: Found on a page of one of our sources