Big Katuna , we have been noticing the same problem with the Corp of Engineer parks. The locals book the weekends from spring until it's too cold (depends where it is) and if you would like a week or two, there are no sites that can be booked! This is thru reservations.gov. Used to be reserveamerica, then they took over their own bookings and it's still happening ! Hate it and they need to do something about it. Sites are sitting empty M-F as people have found somewhere else for their week or two which includes weekends that they wanted.