The Cabin map was a map/blueprint of Jacob's cabin and its location. It was found in a zippered pocket on the dead body of Horace Goodspeed in the mass grave. Horace Goodspeed was presumably the architect/builder of the cabin: in Locke's vision, Goodspeed is seen chopping a tree and said he was "building a place, something for me and the missus." ("Cabin Fever")

Map showing location of cabin on the Island