The few Cornerstone routes worth climbing are best combined with the better destination of Bighorn Dome nearby. Cornerstone is one of the more frustrating features to get to in the park and does not offer much reward for the effort. In contrast Bighorn Dome offers several of the finer 5.10-11 trad routes in the entire park. Any route on Cornerstone that relies on hardware will need to be retro bolted as of 2019 due to every piece being physically obsolete. There is no easy/quick way off the summit. The approach wash/gully is not common or used for any other purpose once you get beyond Bighorn Dome so there is a bit of bushwhacking as well. Listed as north facing in the guide, half of Cornerstone's routes are exposed to the full eastern sun.
All My Children, 5.9*, along with Tomato Amnesia, 5.10b*, form ski tracks on the true north face of Cornerstone and are both stellar tall trad routes. The routes on the east face have bad hardware as of 2019 and/or descriptions in the local guide as, “Loose rock and sparse pro.” Anything outside of the before mentioned two routes did not seem worth climbing which makes this a long hike for two routes. But if combined with Bighorn Dome’s stellar routes, then it makes sense to climb these two for sure. It will make for a significant day out.
Both Bighorn Dome and Cornerstone lay hidden in a wash to the east of the main wash/hike in front of Freak Brothers, Disneyland Dome and Bighorn Mating Grotto. These far eastern objectives are literally the last granite domes to the east before you run into the sloped hills that line the eastern perimeter above Rattlesnake Canyon.
Park as you would for most destinations in Wonderland South, the dirt parking lot just past the large gravel lot for Echo Cove. Drive past where it turns to sand from pavement on Big Horn Pass Road and take a left on a dirt road that leads to a small parking area complete with restroom. Hike north out of the parking area and turn west on a trail heading for the Pink House ruins. Enter the main wash from there and hike a mile until you reach the Freak Brothers feature on your right, which features several large connecting roofs. Turn right after Freak Brothers into a smaller wash and head east. Once you clear the domes on the right and left, look to exit the wash on the left and cross over some flat terrain and enter another wash heading northeast. There is a large boulder with a mixed route on it. Pass under it on the right and boulder hop north until it drops into a wash again. Bighorn Dome is on your left, a north facing wall you will have no visual of until you reach this point. Continue in the wash heading north. This wash is rarely traveled. You will pass below Cornerstone's east face above and left (photo). Continue until you gain the wash that cuts left and then hike up to the base of where the north wall and east wall meet. All My Children and Tomato Amnesia start up steep left facing corners to the right. According to the guide, this is a 2.2 mile hike which seems about right.
Tsunami- 90’-5.10c**/ Way out left by itself, not on the main two walls of the formation. Bad hardware for pro and rap as of 2019.
As the Crag Turns- 100’-5.7*/ Left of two obvious flake systems on the east facing wall. Walk off only as of 2019.
General Hospital- 110’-5.9*/ Right of two obvious flake systems on the east facing wall. Walk off only as of 2019.
Rope Opera- 110’-5.11a*/ Bad hardware as of 2019. Bolted route that finishes at a bolted rap where it meets General Hospital.
One More Leads to Another- 110’-5.10c*/ Bolted variation finish to All My Children, north wall. Walk off only as of 2019.
All My Children- 110’-5.9*/ Exceptional route at the grade. Follow the left ski track up the feature at this right end of Cornerstone. Two cruxes at the grade: the somewhat chossy steep hand/fist crack at the start and after the half way mark you get into some flared fingers. A sloping ledge separates these two sections. Single to #4 and double to #2. Belay/top rope off of a large boulder atop the route on a ledge. To descend, ascend to the summit and scramble down the large gully climbers right. Dow
Tomato Amnesia- 95’-5.10b*/ One of the best 5.10 trad routes in the park offering a lot of variety. Start out in steep large hands and pull a bulge via fingers. Then up the right leaning finger corner with positive holds showing up along the right. Then up an arcing finger crack that turns into a tricky slab ramp to reach chossy face to finish upon the same ledge as All My Children. Same rack as All My Children and same descent option. Dow