It includes a number of ski descents covered in Fifty Classic Ski Descents of North America, a book published by Capitol Peak Publishing in 2010.
The book was edited by Chris Davenport, Art Burrows, and Penn Newhard, with significant contributions from mountaineers who skied many of the listed descents.
Contributors included Jimmy Chin, Pete Costain, Lou Dawson, Kristoffer Erickson, Lorne Glick, Greg Hill, Andrew McLean, Hilaree O'Neill, Eric Pehota, Glen Plake, Kevin Quinn, Chic Scott, Lowell Skoog, Ptor Spricenieks, Mark Synnott, and Jon Walsh.
Two mountaineers, at least, have worked ahead towards skiing all of these, but have made a point to call it folly, if they were to ignore safety considerations merely to bag another descent on the list.
[2] The corresponding term peak bagging, about quests to ascend all mountains in a defined set, is likewise pejorative.