From what I understand of the history, Yosemite Decimal System (YDS) grades came about when class 5 in the preexisting system was subdivided into 5.0 through 5.9. This was done by Chuck Wilts, Royal Robbins, and Don Wilson, who were members of the Rock Climbing Section of the Angeles Chapter of the Sierra Club, as part of Wilts's 1956 guidebook to the Tahquitz Rock area. A particular climb served as the original definition of each decimal point. Wikipedia states that The Trough was the original definition of 5.0, while Open Book defined 5.9. What was the list of ten climbs that defined these grades, and what grades are they considered to be?
Related: Please Explain Rock Climbing Grades