Did Ontario and Cucamonga as a single hike along with Etiwanda and Bighorn for the full ECBO experience. Total distance was roughly 19.25 miles and a total hiking time of 10 hours plus stops at the peaks. Beginning at the Icehouse Canyon trailhead, the order was Cucamonga, Etiwanda, Bighorn, and then Ontario before returning to trailhead. The hike was challenging but enjoyable.

Trail conditions were good except for the section leading up to Bighorn from Cucamonga; for all intents and purposes it's basically off trail on loose dirt with a very steep incline. Poles are very highly recommended for that section. Beginning at 6:00am, the trail to Cucamonga was fairly crowded (we got the last parking spot in the lot) with groups moving at various speeds. Most were good about letting people pass. The trails between Cucamonga and Etiwanda, Cucamonga and Bighorn, and  Bighorn to Ontario were all much less crowded. I was surprised at how few people we saw on our way up to and down from Ontario, but since it was our fourth peak of the day it's possible that most people aiming for Ontario had come and gone by the time we reached that trail.

If you choose to do the full ECBO route, TAKE LOTS OF WATER. My partner and I each took 3 liters but ran out with about 3.5 miles left to go. We really should have each brought 4. We've done hikes of this distance before and felt confident that 3L was enough, but were obviously wrong. It made for an unpleasant final 90 minutes or so, though if we had remembered to bring our filters it wouldn't have been a big deal.

Unfortunately, we weren't able to find the geodetic survey markers on the peaks.