My old log house( 1860s) has a sort of floating floor system with sleeper logs and tongue and groove pine flooring over an unconditioned crawlspace. I’ve been told the house probably originally had a dirt floor only and then later on the wood floor was added. The sleepers do not tie in to the walls and there is about a 2″ gap between the walls and flooring. Any recommendations on what to insulate with, should I just stuff some rockwool in the gaps? We live in Maryland and you can just feel that cold air pumping up through those gaps. 
Eventually I plan to install some nice thick Baseboard Molding to cover up the gaps, just have bigger problems to tackle before worrying about that.