Historian Powell Casey extensively researched the history of Military Road (La. Hwy. 21) and once gave a presentation to the St. Tammany Historical Society detailing his findings. He later published a more extensive report in a statewide historical publication, and I wrote a newspaper article summarizing it. Click on the image of the article below to view a larger version of it.
This historical marker is in Columbus, Mississippi. Jackson's Military Road, surveyed by Captain Hugh Young, ran from Cotton Gin Port to Madisonville, LA. Photo Source: MississippiMarkers.com