October 27, 1847
The members of the legislature, having met on October 18, passed an act providing for an election of delegates to a constitutional convention.
Nation and worldGrade A · 1 independent source
The evidence
“On September 27, 1847, the governor issued a proclamation, calling a special session of the legislative assembly, to be held at Madison, October 18, 1847, to take action in relation to adopting a constitution and forming a state, and as to its admission into the Union. The members of the legislature met, in pursuance of the proclamation and, on October 27, passed an act providing for an election of delegates to a constitutional convention to be”
1908-brown-rock-county/05-historic-evolution.md, Vol. 1, PDF p. 138 / book p. 123
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