"I climb 5.9" was inspired by a conversation about a piece of climbing history. Back in 1952, at 17 years old, Royal Robbins did the first free ascent of a route called Open Book. It was one of the hardest routes in the country and became the first climb given a grade of 5.9 on the Yosemite Decimal System. (The Yosemite Decimal System is a set of numeric ratings describing the difficulty of climbs, primarily used by rock climbers in the United States and Canada.) As technology and the sport of climbing have progressed, so have the difficulty of the grades. But in 1952 a 5.9 was the most difficult, and well deserving of rock respect.