In May of 1840 General Joseph Montfort Street died. General Street had been Indian Agent to the Sacs and Foxes, and by all accounts had looked out for the interests of the Indians. He had a close friendship with Wapello and with Poweshiek. He was buried at the site of the Indian agency near what is now called Agency, Iowa. Here is a look at his gravestone.
This information is from a historical marker nearby.