Some day, I'd really like to ride the Haul Road (aka the Dalton Highway) from Fairbanks up to Deadhorse on the Arctic Ocean. When I do, this looks to be the craziest climb on the route, especially given that it's unpaved. The Northern side doesn't seem to be anywhere near as difficult.
Atigun Pass South is located in Alaska. It is 2991.3 meters long with an average gradient of 11.8% and a maximum gradient of 28.4%. Find similar hills.