Hey @MarkH - thanks for the question! Our (REI's) DC Monuments tour is always so popular, hits capacity just about every time! I believe our outdoor school is running some of the last sessions of the season this weekend (before the weather turns). Stay tuned for the first spring sessions - these classes and tours can be booked on REI.com! In the meantime, have you checked out the Ghosts of the Potomac kayak tour? It includes travel to and from Mallow's Bay and, when I checked this morning, there was still a spot available.