February 28, 1839
An amending act was approved fixing the time for the election of county officers.
Nation and worldGrade A · 1 independent source
The evidence
“By a law approved February 13, 1839, it was enacted, " that from and after the passage of this act, the county of Rock shall be and remain to all intents and purposes, an organized county of this Territory, and shall have all the rights and privileges which organized counties in the same of right have." An election of county officers was provided for, to be held " on the first Monday of March, 1889," and the officers then chosen were empowered to borrow money on the credit of the county, not exceeding $250, for three years, at 12|^ per cent per annum, to be applied to procuring land for the seat of justice. By an act, approved February 28, 1839, the foregoing was so amended as to fix the time for election of county officers for the”
1879-history-of-rock-county/09-rock-county-ch03-pioneer-reminiscences.md, PDF p. 353 / book p. 357
Butterfield, C. W., et al. The History of Rock County, Wisconsin: its early settlement, growth, development, resources, etc. Chicago: Western Historical Company, 1879. Cornell University Library via the Internet Archive, archive.org/details/cu31924028871585.
Grade A: Found on a page of one of our sources