Lake Corner, the Upper Yellowstone and Shoshone Drainages Professional Review and Guide
"Most of this section deals with the headwaters of the Yellowstone River and Yellowstone Lake. Much of the eastern boundary of Yellowstone National Park was determined in an exchange many years ago of USDA Forest Service and National Park Service lands to conform to drainage boundaries in the area. The southeast corner of the park was left in its original rectangular state.
The other major exception is the East Entrance corridor. From the crest of Sylvan Pass 6.5 miles east to the East Entrance, the park retained part of the Shoshone River drainage. This stream, Middle Creek, joins the North Fork of the Shoshone just outside the park at Pahaska Tepee. The Shoshone, in turn, collects much of the drainage from the east flank of Yellowstone National Park while heading east to join the Bighorn River in north central Wyoming. This eTrail contains information on Middle Creek, The Thorofare, Atlantic Creek, Bridger Lake, Thorofare Creek, Yellowstone Lake, Sylvan Lake, Clear and Cub Creeks, Bear and Sedge Creeks, Pelican Creek, Riddle Creek, Chipmunk Creek, Duck Lake, and Yellowstone River (Fishing Bridge to Chittenden Bridge)."