The valley is traversed by several highways, including U.S. Highway 285, which enters the valley from the eastern side over the Front Range at Kenosha Pass, providing a vehicle link to Denver. The highway crosses Red Hill at Red Hill Pass. On its northern side, the valley is connected by several high mountain passes to the valley of the North Fork of the South Platte River (a tributary of the South Platte). It is also connected by CO Route 9 via Hoosier Pass to the valley to the Blue River near Breckenridge. To the west, the extremely high Mosquito Pass crosses the Mosquito Range to Leadville. (Mosquito Pass is no longer a practical transportation route, but is now a historical and recreation site.) On its southwestern side, at the southern end of the Mosquito Range, it is connected by Trout Creek Pass to the upper valley of the Arkansas River near Buena Vista. U.S. Highway 24 enters South Park from the east at Wilkerson Pass, where the highway provides vehicle access to Colorado Springs. To the very south, CO Route 9 crosses Currant Creek Pass, which marks the southern edge of the South Park region.