Located alongside the Potomac River is the historic C&O canal. It is my dog’s all favorite time walk. He and I have wandered three different segments of the Canal. It was the first super-highway built in the US. Well, compared to today’s superhighways it was less than they are, but still a massive improvement. You could move more goods between the two connections via the water than you could by horseback.
The many canals built in the US began to fall into disrepair over the years. They stopped being relevant with the rise of the steel horses. First, the steam locomotives were able to pull more people, cargo and do so much faster than a mule walking alongside a canal pulling a barge (there were normally two mules, one on each side pulling the boat). It was often a one-way route, not much room to allow two barges to be in the same place.
Because of the nature of the canal, it had locks to keep the water flowing at the same level. The locks, which on the river itself were rapids, allowed the boat and cargo safe passage. The rapids were dangerous, and in the spring with the rains, they were deadly. The canal smoothed that rush of water by avoiding it completely. The Potomac flows between Maryland and Virginia and loses about 1000 feet in elevation as it approaches Washington DC.