1837
Caleb Blodgett erected a house of boards, the product of Goodhue's mill — the beginning of the Rock River house.
The propertyGrade A · 1 independent source
The evidence
“Atwood and her daughter, in the summer of 1838, arriving here on the 25th of June of that year. My father had returned to Beloit in November, 1837, but did not bring his family because there was then no place to put them. There were only three log houses in the town in 1837 and those were all occupied by the male workers who were preparing the ground for their wives and children. In 1837 Caleb Blodgett erected a house of boards, the product of Goodhue's mill. This was the beginning of the Rock River house, situated where the Goodwin house now stands.”
1908-brown-rock-county/06-history-of-beloit.md, Vol. 1, PDF p. 155 / book p. 139
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