Naches fire Chief Dan Mansfield said the woman, who authorities did not identify, fell about 15 feet while climbing with a companion.
Firefighters placed her in a stretcher and carried her out to the highway and a waiting ambulance. She was taken to Yakima Regional Medical and Cardiac Center for treatment.
Mansfield said the fall, which happened about 12:15 p.m., occurred a half-mile off the highway at about 24 miles east of the summit of White Pass.
Naches firefighters responded and received mutual aid from the Yakima Fire Department and the Yakima Training Center Fire Department.