I think it's mostly in the Sierra Nevada in Califormia. See the below link for an interview Greg Child did with him. There was also an article with photos of some of the ridge climbs in Alpinist magazine, Issue 20 I think, but article not available on their web site.
Yes. It might be a knife-edge ridge that goes for miles. It might be of Himalayan scale but it does not have the commitment or risk of being in the Himalayas. One of the best things I have done is in the Evolution area of the Sierras. It is seven miles of ridge climbing. I climbed it with tennis shoes and a light pack. It followed the crest of dozens of peaks.