Summer 1833
The United States began the surveys of this part of Rock county; the portion of the town of Janesville west of the river was surveyed first.
Rock CountyGrade A · 1 independent source
The evidence
“The United States began the surveys of this part of Rock county in the summer of 1833. The portion of the town of Janesville west of the river was first surveyed. The town lines were run by surveyors, Mullet and Brink in the third quarter of 1833, and the sections and subdivisions were surveyed later in the same year by George W. Harrison.”
1908-brown-rock-county/26-history-of-janesville.md, Vol. 2, PDF p. 10 / book p. 525
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