@ SVCarolena, I wasn't aware that the Potomac froze over. I figured there would be some ice along the edges, and perhaps some chunks floating downstream which would present a hazard to a boat at anchor, but I guess I thought the Potomac had enough current and volume for it to freeze.
Then again...I suppose a long enough freeze and it certainly would/could freeze over. We are quite new to the area, and I feel like a sponge soaking up all the info everyone is providing!
It isn't consistent from year to year. As mentioned, this last winter was very cold with tons of snow and things did freeze up for a bit. Other winters you may get only a bit of ice along the edges. Keep in mind that near DC there isn't a lot of current and the water is basically fresh. Current picks up the further south you go, as does the salinity.