Casler hardware 2, photo by tstevensphoto.

The photo is part of Travis’s Jackson, MI set (slideshow). The marker denotes the location of the Jacksonburg Public Square – click through for full text of this marker and map of the location.

The best history online I’ve found is Jackson: The First One Hundred Years, 1829-1929 from the Ella Sharp Museum. It says, in part

Over one hundred and fifty years ago, a young New Yorker named Horace Blackman, a frontiersman from Ann Arbor and a Pottawattomie Indian guide, camped on the west bank of the Grand River at the intersection of what is now Jackson Street and Trail Street in the city of Jackson, Michigan. Blackman had been ‘spying out the land’ looking for a ‘location.’ Satisfied with what he saw, he purchased a quarter section and registered his one hundred and sixty acre claim. Several months later, he built himself a log cabin and then went home to collect his family, having become the founder of a future city.

…Jackson-for this is what the village would be called, after brief encounters with the names ‘Jacksonburgh’ and ‘Jacksonopolis’– had location. As the Indian trails clearly indicated, it was a cross-roads-a point through which people, ideas, information and materials going in various directions passed. Now, at a time when transportation had become a critical organizational link between the nation’s eastern populations and the frontier’s seemingly limitless resources and wealth, Jackson was in a position to benefit.

You can get much more at the link above and also check out Jackson, Michigan in Wikipedia.