Sandra J. Worden, 74, and her passenger, 76-year-old Patricia Craven, of Lathrop, Mo., were both taken to St. Alphonsus in Eagle after the Sunday afternoon rollover.
On Monday afternoon, Worden was in critical condition and Craven in fair condition, a spokesman for Saint Alphonsus in Boise reported.
Idaho State Police said Woden was headed north on Idaho 55 near milepost 70 about 1:30 p.m. when she drove off the right shoulder of the road, rolling the car down an embankment. It came to rest on its roof.
Police said both women wore seat belts at the time of the crash.