McMahon’s Mill is located at mile 88.1 on the C&O Canal. A little research into the structure shows it listed, over the years, as Avis Mill, Charles Mill, Cedar Grove Mill, and McMahon’s Mill, but until about four months ago it was off limits to the public. The reason, of course, is that the area was a staging and operations center while work was being done on the Big Slackwater Project. The mill and waterfall are both as picturesque as ever, but much of the rest of mill grounds are new-and-improved. There are a number of new signs that tell the story of the project, and still more can also be found near Guard Lock 4 (downstream). In fact, the entire area once bypassed by the detour is pretty well labeled with interpretive signs and markers. As for the mill, the parking lot looks like it will hold fifteen or more cars, and a section of the stream bed has been lined with large chunks of gravel. In all, a hike from McMahon’s Mill to Dam 4 is an enlightening experience for those interested in the former operations of the Chesapeake and Ohio Canal.