When Is The Rock County Fair 2025. June 21, 2025 @ 11:00 pm website: This year’s fair starts tuesday and runs through sunday, july 28, at the rock county fairgrounds in janesville with the theme of “a treasure chest of rock county’s best.”

June 20, 2025 @ 10:00 am end: This year’s fair starts tuesday and runs through sunday, july 28, at the rock county fairgrounds in janesville with the theme of “a treasure chest of rock county’s best.”