September 28, 1857
The State Fair was held at Janesville.
The evidence
“The next State fair held at Janesville began September 28, 1857, and closed October 2. The annual address was delivered by Prof J.”
1879-history-of-rock-county/12-rock-county-ch06-politics-war-record.md, PDF p. 449 / book p. 453
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
“The next state fair held at Janesville began September 28, 1857, and closed October 2. The annual address was delivered by Professor J.”
1908-brown-rock-county/17-agriculture.md, Vol. 1, PDF p. 444 / book p. 411
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 · may repeat 1879-history-of-rock-county, so not counted as independent