I would not guess that there were a lot of people in that area of Wisconsin in 1815. Chicago wasn’t founded until 1830. Fort Dearborn was built in 1803, but was burned down in 1813.
French Voyageurs (trappers) and Jesuit explorers/missionaries were here.
I was thinking the same thing. They'll have to clean it up to determine it's real age. But my guess is that it belong to a French trapper.
Wisconsin Territory
Wisconsin Territory was created by an act of the United States Congress on April 20, 1836. By fall of that year, the best prairie groves of the counties surrounding Milwaukee were occupied by New England farmers.[14] The new territory initially included all of the present day states of Wisconsin, Minnesota, and Iowa, as well as parts of North and South Dakota. At the time the Congress called it the “Wiskonsin Territory”.[15]
The first territorial governor of Wisconsin was Henry Dodge. He and other territorial lawmakers were initially busied by organizing the territory’s government and selecting a capital city. The selection of a location to build a capitol caused a heated debate among the territorial politicians. At first, Governor Dodge selected Belmont, located in the heavily populated lead mining district, to be capital. Shortly after the new legislature convened there, however, it became obvious that Wisconsin’s first capitol was inadequate. Numerous other suggestions for the location of the capital were given representing nearly every city that existed in the territory at the time, and Governor Dodge left the decision up to the other lawmakers. The legislature accepted a proposal by James Duane Doty to build a new city named Madison on an isthmus between lakes Mendota and Monona and put the territory’s permanent capital there.[16] In 1837, while Madison was being built, the capitol was temporarily moved to Burlington. This city was transferred to Iowa Territory in 1838, along with all the lands of Wisconsin Territory west of the Mississippi River.[17]
https://en.wikipedia.org/wiki/History_of_Wisconsin
Yeah, it would have been mostly French trappers in the area at that time.
Just my guess but it looks like the remains of a `trade musket’ which were carried mostly by Indians.