Deer Mountain is one of the few peaks in Rocky Mountain National Park that has a trail leading to its summit. What makes it even more attractive is its short round-trip distance and relatively moderate vertical climbing. While this remains a popular hike for these reasons, the limited parking at the trailhead helps to control the crowds.
The trail starts climbing immediately over the first mile through open wooded areas where you'll pass an access trail to reach Aspenglen Campground. After roughly a half mile, the trail opens into open meadows with views of the valleys and overshadowing mountains within Rocky Mountain National Park.
After about 0.8 mile, you'll reach the first true switchback. Be careful not to miss it. Know to keep your eyes peeled uphill once you hit the open meadows. After a couple switchbacks through open meadows offering vast views of multiple sides of the park, you'll enter a densely wooded area that is more rocky. You'll reach somewhat of a false summit before heading back downhill for about a mile. Don't worry, this means you're getting close! After reaching the intersection with the trail leading down to Estes Park, you are a short rocky stair sprint away from the true Deer Mountain summit.
The Deer Mountain Summit is open and rocky. You'll be treated to unique views down at the east entrance of park as well as Estes Park behind it. As you explore the summit, you can move around clockwise to the south-southwest facing vistas offering a new view of the valleys and taller peaks on that side of the park.
It is easy to see why this is a popular hike, so be sure to arrive for sunrise if you wish to avoid congestion.