Twin Sisters Peaks, Mountain summit in Rocky Mountain National Park, Colorado, US

Twin Sisters Peaks is a two-summit mountain formation in the Front Range of Colorado, with the two tops linked by a rocky, boulder-covered saddle. The formation sits on the eastern edge of Rocky Mountain National Park and rises clearly above the surrounding forest.

Locals in Estes Park first called the mountain Lily Mountain; the name Twin Sisters Peaks was submitted to the Washington Geographic Board on March 7, 1907 by Ellsworth Bethel. The first trail and a fire lookout were built in 1914, and in 1917 the mountain was officially made part of Rocky Mountain National Park's eastern boundary. Swiss mountaineer Walter Kiener was the first RMNP ranger to operate the lookout, serving five summers.

The peaks are a common starting point for people who want to gain confidence on mountain terrain before moving on to more demanding routes in the region. On weekends, the trail sees a steady flow of hikers of all levels, from families to more experienced climbers.

The trail to the summits takes around 4 hours round trip and crosses open, exposed sections where weather can shift quickly, especially in the afternoon. Starting early in the morning gives hikers the best chance of reaching the tops before storm conditions develop.

The summit ranger station was razed in 1977, but its remains can still be seen at the top. The first fire lookout was set up there in 1914, and Swiss mountaineer Walter Kiener was the first Rocky Mountain National Park ranger to staff it, serving five summers and drawing more hikers to the trail.