The route starts at Catherine Lake. This can either be reached from Thousand Island Lake or from the North Fork of the San Joaquin River. From the NW side of Thousand Island Lake, follow a use trail towards North Glacier Pass. Eventually branch off towards the pass and cross the North Fork of the Creek so you are between the two branches (see map). You may be able to find a use trail, if not just head towards the narrow band of snow that connects the two snowfields right below the pass. When you get to this point, you can either cross the small section of snow to the rocks, or stay on the left snowfield and head more to the left. When you get to North Glacier Pass do not go down to Catherine Lake.
Stay high and head towards the long, thin snowfield that leads up to the ridge above the main Glacier. Cross this snowfield low and start heading up towards the higher snowfield. Angle up to the right . If you hit a gully that deadends, go back slightly and to the right where you can pull yourself up. Once you get near the highest snowfield, head right around the snow and then up to the highpoint at the base of the sheer cliffs of Banner. At this point head down a little bit, following the base of the cliff. You might begin to see cairns at this point. If not just stay at the base of the cliff until you can descend a little bit towards the glacier. Head up a little bit from here where you will hit the glacier just below the Ritter/Banner Saddle. Head up the glacier towards the rocks, then follow the rocks towards the saddle. When you find a good place, peel off to the left and head up the west slope of Banner where you will have a slog to the top.
An ice axe and crampons would be useful for the short glacier section, but it's not too steep. If you have this gear you might be better off just going around Lake Catherine to the glacier and following it up to the saddle.
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