7:04P.M. for 22 minutes
I love this park, but today was not the best day to visit it. Apparently, late July is when the midges come out in great swarms. Literally every few yards of the rail, a dense cloud of dozens of midges swarmed at head-height. I got in a walk, and thanked the gods of fortune that I wore my broad-brimmed hat, but it was something of a trial.
On the other hand, I met a deer on the golf course that you have to traverse to visit the park. It just looked at me as I approached, and let me get within a few feet before it pranced a few dozen feet away. Magical.
I should explain that odd feature of the park. Your GPS will direct you to a cul-de-sac in a residential neighborhood. You have to take the unamrked road to your right, around the back of the houses, where you'll find a parking lot big enough to fit about 20 cars, right next to a golf course. You'll then have to walk through the golf course, along cement paths with signs pointing you to the park.
The park itself is a strip of land along the Potomac River that connects to several other parks. You can just walk for hours along simple dirt paths.