The Billy Goat Trail, on the Maryland side of Great Falls, is extremely popular and, therefore, extremely crowded. That's one reason we decided to visit it on a very cold day with a snowstorm predicted to move in that night.
We got a later start than was ideal, so we didn't reach the park until the afternoon. From the parking area, the C&O Canal towpath heads east and west; we went east towards the falls. We then headed out to Olmstead Island, which is an easy boardwalk path with nice views of the falls. We then used the towpath to reach the start of the Billy Goat Trail. It is now one-way, so we hopped on at the entrance and began scrambling over boulders.
Because of our late start, we opted to use the exit trail before Purplehourse Beach, returning via the towpath. I think that was the right call - I'd rather be able to enjoy this hike than rush through it.
https://www.flickr.com/photos/turducken/51828137410/in/datetaken-public/Our loop was a total of 4.5 miles.