The D1 is the original technical climbing route up the Diamond of Longs Peak.

In 1954, when National Park Service was petitioned to allow climbing on the Diamond they responded with an official closure.

When the ban was lifted later that year, Dave Rearick and Bob Kamps were the first to climb the Diamond via a route that would come to be known simply as D1.

[1] This route would later be listed in Allen Steck and Steve Roper's influential book Fifty Classic Climbs of North America.

[2] Today the route is not necessarily regarded as the best of its grade on The Diamond, some consider other routes to be of higher quality.