Heading north (upstream) from its mouth, the major branches of the Skagway River are as follows: 1-East Fork: The East Fork branches off the Skagway River, opposite Mile Post 4.8 of the White Pass railroad. At Mile Post 5.8, the railroad makes a U-turn, crosses the East Fork, and loops back to follow the main river. 2-White Pass Fork: The Skagway River turns to the east and White Pass Fork branches off to the north, opposite Mile Post 12 of the railroad. At Mile Post 14.2, the railroad makes a U-turn, crosses the Skagway River, and loops back to follow White Pass Fork. 3-Cut-off Gulch: White Pass Fork splits into Cut-off Gulch to the east and Dead Horse Gulch to the north, opposite Mile Post 18 of the railroad. At Mile Post 18.6, the railroad makes a left turn and crosses Cut-off Gulch. 4-Dead Horse Gulch: After crossing Cut-off Gulch, the railroad goes through a tunnel which comes out along Dead Horse Gulch. The head of Dead Horse Gulch is at Pump House Lake, at Mile Post 20 of the railroad.