Entry No. 172 — the Denver file — filed under: outdoor
Sleepy Lion Trail to Button Rock Dam
Most people aiming for "a hike near Boulder" never turn down the dirt road to Button Rock Preserve, which is exactly why it stays quiet. You start on a flat service road tracing North St. Vrain Creek past tiny Longmont Reservoir, then the Sleepy Lion Trail peels off and climbs through ponderosa and Douglas fir into a high rolling meadow with views toward Longs Peak and Mt. Meeker. It's named for a ranger who found a mountain lion napping on a rock here. Bighorn sheep, reintroduced in the 1980s, and wintering elk move through these slopes. The loop closes at Button Rock Dam, where water roars off a granite cliff into a pool. Big country, almost nobody on it.
The story
Tucked off Boulder County Road 80 a few miles west of Lyons, Button Rock Preserve isn't a state park or a county open space—it's a protected municipal watershed owned and managed by the City of Longmont to safeguard its drinking supply in the Ralph Price Reservoir. Because of that status, cars, mountain bikes, and drones are banned past the entry gate, leaving the narrow granite canyon of North St. Vrain Creek mercifully quiet compared to the clogged trails around Boulder.
The Sleepy Lion Trail owes its name to a real encounter when a local field ranger crested a rocky ridge and stumbled onto a mountain lion comfortably napping on an exposed boulder. The trail peels off the flat service road about three-quarters of a mile in, climbing through Deadman Gulch under ponderosa pine and Douglas fir before opening into a high rolling meadow. Up top, the forest gives way to unobstructed views of Longs Peak and Mt. Meeker, while reintroduced bighorn sheep and wintering elk move across the upper slopes.
The loop drops back down to the base of Button Rock Dam, where water drops off a towering granite cliff directly into a churning plunge pool. During late spring and early summer snowmelt, the spillway releases a thunderous rush that coats the footbridge in heavy, cold mist—a dramatic finish to a trail that most Front Range weekenders walk right past.
What it's like
Arriving at the gated gravel lot on Longmont Dam Road requires early timing on weekends; the 60-space lot fills fast, and local enforcement strictly tickets or tows roadside overflow. You'll start on a flat dirt service road following North St. Vrain Creek alongside quiet fly fishers before spotting the Sleepy Lion trail sign on your left. The singletrack climbs through dirt, rock, and exposed roots—keep an eye out for small wooden arrows tacked to trees near the upper ridge where the trail turns rocky. Since May 2023, dogs are strictly banned anywhere in the preserve to protect the watershed, so leave your pets at home. Bring layers and plenty of water, and watch the afternoon sky closely; storm clouds build rapidly over the divide in summer.
The move: Skip the crowded flatirons-selfie hikes and make the drive itself the date. Pack water and a snack, leave the dog at home (not allowed here), and walk in past the gate together. The first easy stretch along the creek is for talking; the climb up Sleepy Lion is for working a little; the meadow at the top is where you stop, sit, and watch for bighorn while the whole Front Range opens up. Finish at the dam, feel the spray, and let the quiet do the rest. A real adventure that takes a half day, not a whole one.
📍 Before you go Full loop is roughly 5 miles round trip with about 850 ft of gain, rated moderate; the first half-mile is flat service road before the real climb begins. Trailhead: from Lyons, US-36 west ~4 mi, left on Boulder County Road 80 ~3 mi to the gated lot (about 45 min from central Denver). Free entry, no permit to hike; a separate fishing permit is required only for Ralph Price Reservoir. No dogs allowed in the preserve since 2023 (watershed protection). Best from late spring through fall — wildflowers and wildlife peak in spring/early summer. The northwest section closes Dec 1–Mar 31 to protect wintering elk, and snow, ice, and afternoon mountain storms are real risks shoulder-season and summer; carry layers and water, and turn back if thunder builds. The lot holds about 60 cars and fills early on weekends; roadside parking gets ticketed or towed.
- 📍 Lyons / Button Rock Preserve (northwest of Boulder)
- 💸 Free
- ⚡ Up for anything
- 🌗 Outdoors
Where: Button Rock Preserve Trailhead, Lyons. From Denver/Longmont, take US-66 west to Lyons, then US-36 west ~4 miles, turn left onto Boulder County Road 80 (Longmont Dam Road) and continue ~3 miles to the gate. Park in the lot at the gate (about 60 cars, fills early on weekends); the preserve is walk-in only past that point.
Hours: Day-use, free. Best season: Late spring through fall. Confirm trail & road conditions before you go.
⚠ Seasonal or scheduled — always check before you go.
Pair it with
- Lyons Memorial Labyrinth — After wrapping up your loop along North St. Vrain Creek, drive four miles into Lyons to walk this quiet riverside labyrinth built from cobbles deposited by the 2013 floodwaters.
- The Speakeasy (Imperial Hotel basement) — Since Longmont owns and manages the Button Rock watershed, cap off your outdoor outing in downtown Longmont with a drink in this subterranean 1881 basement lounge.
- Seven Keys Lodge Key Room (formerly Baldpate Inn) — If you continue west up US-36 toward Estes Park, stop at this historic lodge to browse a floor-to-ceiling collection of over 20,000 donated keys from around the world.
- Saul the Sticker Ball (StickerGiant lobby) — Pair your mountain hike with an offbeat roadside stop in Longmont to see a 231-pound Guinness World Record ball covered in over 171,000 stickers.
Good to know
How long is the hike and how difficult is it?
The Sleepy Lion to Button Rock Dam loop is roughly 5 miles round trip with about 850 feet of elevation gain. It's rated moderate, starting flat along a river service road before narrowing into a rocky singletrack climb.
Are dogs allowed at Button Rock Preserve?
No. As of May 15, 2023, dogs are strictly prohibited throughout Button Rock Preserve to protect Longmont's drinking watershed and local wildlife.
Do I need a permit or fee to visit?
Entry and parking are completely free, and no hiking permit is required. However, if you plan to fish in Ralph Price Reservoir, a separate City of Longmont fishing permit is required alongside your Colorado fishing license.
When is the trail open?
The preserve is open year-round for day use, though the northwest section closes annually from December 1 to March 31 to protect wintering elk. Late spring through fall offers the best conditions.
Plan a visit & invite your people →
Further reading: hikingproject.com · Official site · longmontcolorado.gov
last checked: 2026-06-10