The song is about one of so many historical events that could, if they were much better known, have a real impact on the outlook of so many people, about the prospects for civilization.
Anti-slavery sentiment was so strong in the state of Wisconsin that it was never necessary to institute military conscription there during the US Civil War.
In the decade prior to the Civil War, Congress passed the Fugitive Slave Act in 1850, which legally required authorities in states where slavery was banned to return people who had escaped back to those who claimed to own them.
There was only one attempt to enforce this law in Wisconsin, and it resulted in the captured, formerly enslaved man, Joshua Glover, being freed from the jail in Milwaukee by a crowd of thousands of local people, who then protected Glover and made sure he had the means to get to Canada, where he could be beyond the jurisdiction of the slaveowners.
"In Wisconsin in 1854 (Song for Joshua Glover)" REMIX