Rock County was fully organized (a different reading from the February 13 organization act above and the spring organization below).

The evidence

• “The city of Janesville is the county seat. Rock was set off from Milwaukee county, December 7, 1836, and fully organized February 19, 1839, It is composed of twenty organized towns, of six miles square, each— 720 square miles—460,800 acres.”

  1856-history-of-rock-county/03-rock-county.md, PDF p. 41 / book p. 23

  Guernsey, Orrin, and Josiah F. Willard, editors. History of Rock County, and Transactions of the Rock County Agricultural Society and Mechanics' Institute. Janesville, Wis.: William M. Doty & Brother, 1856. Cornell University Library via the Internet Archive, archive.org/details/cu31924028871593.

  Grade A: Found on a page of one of our sources