This is not a hard trip
It is about 95 n/m from Point Lookout to Washington. It takes me a week, but I poke around on purpose. As Jim points out, the river is "different" north of what is known as "the 301 bridge," the halfway point between the Chesapeake and DC. It is more shallow, but the channels are plenty deep - tugs and small cruise ships run up and down the river all the time. There is also a Navy Base in DC with BIG ships in it. OK, they never leave but they got up there somehow.There is a book entitled "Discovering the Tidal Potomac." I can't remember who wrote it but it is very good, aside from the fact that it is written "south," from the perspective of someone sailing from DC to the mouth of the Potomac. Has lots of sightseeing and fairly up to date Marina information, including phone numbers.Why would you want to do this trip at night? It is a very pretty trip - take your time and smell the roses. I for one would not travel in such close quarters in the dark without "local knowledge," but it is no more or less safe on the Potomac than anywhere else. And FWIW, the bottom is mud - only your pride is at risk.I will respectfully disagree with Jim on the rent-a-car from Cobb Island idea. I recommend you sail in the dark, drinking heavily, before you even consider driving anywhere around Washington, DC. Hotels are also very expensive in DC - you can anchor is Washington Channel for nothing.Google the book.