There are numerous Treasure Maps hidden within Ultima IX.
Buccaneer's Den Maps
All three of these maps can be bought from the catographer of Buccaneer's Den. The first shows a hidden well beside Samhayne's house leading to treasure. The second shows a cannon that has to be fired two times to get the Gauntlets of Fury. The third shows the cave of the Silver Serpent.
Pirate Treasure Map
Training Book Map
This map is found behind a tombstone in the graveyard in Cove. It shows the location of the underwater tomb of the swordmaster who was buried with the training book for the last 2-handed technique at 1° 23' north, 52° 3' west.
Treasure Island Map
This map is found in the cave leading to the Shrine of Honesty on Verity Isle. It shows a small island at 0° 4' north, 63° 4' east, with a treasure chest that besides other things contains a part of the Bone Armour.
Map to Star of Britannia
This map is found tucked into the supports of the entrance to the Mathis Mines west of Yew. The Marked Location is a cave on the isle southeast of Trinsic at 86° 50' south, 9° 58' west, within which lies the Star of Britannia, needed to be traded for the last staff technique.