Must have misheard as 51 doesn't go anywhere near Natchez. Highway 51 parallels I-55 N/S pretty much down the middle of the state from TN to LA. He most likely said 61 as Highway 61 indeed runs through Natchez, and meets Highway 84 right outside town, at Washington, not to far away also meets the Natchez Trace National Parkway at it's official beginning. Used to be nightmare, but got improvements, especially during the 84 4 lane project! Now its a smooth 4 lane route all the way thru! I spent many, many hours on the strip between 553 in Fayette, and Natchez.