Boulder Grand Pass, Wild Basin Trailhead, Rocky Mountain National Park, Colorado

Boulder Grand Pass - 14.5 miles

Wild Basin Trailhead

View down the East Inlet Valley from Boulder-Grand Pass (12,061')

View down the East Inlet Valley from Boulder-Grand Pass (12,061')

Round-Trip Length: 14.5 miles (distance will vary by route)
Start-End Elevation: 8,510' - 12,061' (12,061' elevation @ pass)
Elevation Change: +3,551' net elevation gain (3,875' total roundtrip elevation gain)
Skill Level: Strenuous
Dogs Allowed: No
Bikes Allowed: No
Horses Allowed: No
Related Trails:

Boulder Grand Pass - 14.5 Miles Round-Trip

Boulder-Grand Pass (12,061') is located 7.25 miles from Wild Basin Trailhead in Rocky Mountain National Park. It spans a broad saddle along the Continental Divide between Tanima Peak (12,420') and Pilot Mountain (12,222').

Trail Map | Photo Gallery

An unmaintained but well-established trail continues 1.45 miles and 1500' above Thunder Lake to Lake of Many Winds and a near-vertical climb to the pass.

Views are stunning, particularly west down the East Inlet Valley to Fourth Lake, Spirit Lake and Lake Verna.

A challenging x-country route continues down the East Inlet side and picks up the East Inlet Trail to form a 17 mile thru-hike across RMNP.

The trail between Thunder Lake and BGP is faint in places and can be difficult to follow, though navigation is fairly intuitive up the Lake of Many Winds outlet stream.

Travel beyond LoMW is very difficult: the route climbs 400' in just .15 miles from the far end of the lake on loose scree, dirt and (potentially) snow. Keep space between hikers to avoid falling rock. The descent is equally challenging and requires great care. Only experienced hikers should attempt the pass.

To expedite travel, this description takes advantage of the Backcountry Campsite Access Trail vs. following the main trail all the way to Thunder Lake (see map).

Doing so skips Calypso Cascades and Ouzel Falls, but reduces one-way mileage by .8 miles. Day hikers should follow this route to save time for more demanding and exposed sections above Thunder Lake. Roundtrip distance to the pass on the main trail is 16.1 miles (vs 14.5), a modest but significant difference at these elevations:

The trail rises gently beside North St Vrain Creek past spurs for Lower and Upper Copeland Falls (.35 and .45 miles) to the backcountry campsite access trail split (1.38 miles : 8,860').

Bear right on a variously steep and rocky climb past the Tahosa and Aspen Knoll Campsite spurs to rejoin the main trail (2.65 miles : 9,505'). Grades moderate on a fast and nondescript stretch to the Thunder Lake - Lion Lake Trail split (3.9 miles : 10,025').

The Thunder Lake Trail steepens through a subalpine forest with views of Mertensia Falls across the valley to a bridge (5.05 miles : 10,510').

It rises to a crest at the Thunder Lake Group Campsite spur (5.65 miles : 10,676') and drops to the Ranger Cabin at Thunder Lake (5.8 miles : 10,574').

A well-defined trail continues along the north side of Thunder Lake to a bridge over the inlet (6.05 miles) and weaves through treeline to a large meadow (6.3 miles : 10,830').

It rises up the left side and scales a steep snowfield to regain the trail, then levels across a wide, level bench (6.75 miles : 11,360').

The trail loses clarity here but is intuitively followed to the far side where a steep, twisting push leads to the Lake of Many Winds (6.9 miles : 11,610'). This large tarn is set among rolling alpine meadows with excellent views - a fine place to stop if not aiming for the pass.

Boulder-Grand Pass is located directly above the lake on the right side of the triangle-shaped snowfield embedded in the valley headwall. The trail all but vanishes here as you improvise (right) around LoMW into a large talus field on the west side.

The talus looks formidable (if not impossible) to cross, but it's fairly quick. Scramble through the rock to reach much smaller scree and loose dirt on the far side of the lake, where you'll regain a faint path that heads straight up (7.1 miles : 11,665').

The path turns sharply up and heads to the right of the snow triangle. Terrain is very loose; watch for falling rock and make sure your feet are secure.

The route funnels (right) through a chute and abruptly levels in open tundra at Boulder-Grand Pass (7.25 miles : 12.061').

The pass spans a broad, rolling saddle on the Divide that tilts down to the west. Continue a short distance through the meadows for exceptional views down the East Inlet Valley to Fourth Lake, Spirit Lake and Lake Verna.

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Interactive GPS Topo Map

Key GPS Coordinates - DATUM WGS84

  • N40 12.469 W105 33.993 — 0.0 miles : Wild Basin Trailhead
  • N40 12.230 W105 34.391 — .45 miles : Spur to Upper Copeland Falls
  • N40 12.022 W105 35.293 — 1.35 miles : Backcountry campsite access trail split
  • N40 11.923 W105 35.540 — 1.7 miles : Tahosa Campsite spur
  • N40 12.094 W105 35.839 — 2.0 miles : Aspen Knoll Campsite spur
  • N40 12.304 W105 36.407 — 2.6 miles : Rejoin main trail; bear right
  • N40 12.490 W105 36.960 — 3.15 miles : Fast, moderate travel
  • N40 12.773 W105 37.495 — 3.9 miles : Thunder Lake - Lion Lake Trail split
  • N40 12.808 W105 37.910 — 4.4 miles : Transition into subalpine forest
  • N40 13.236 W105 38.233 — 5.05 miles : Cross bridge over tributary
  • N40 13.343 W105 38.691 — 5.8 miles : Thunder Lake (10,574')
  • N40 13.429 W105 38.962 — 6.05 miles : Cross Thunder Lake inlet stream
  • N40 13.445 W105 39.314 — 6.3 miles : Enter large meadow
  • N40 13.443 W105 39.460 — 6.55 miles : Top of steep snowfield
  • N40 13.448 W105 39.767 — 6.75 miles : Steep push through open alpine
  • N40 13.454 W105 39.879 — 6.9 miles : Lake of Many Winds
  • N40 13.522 W105 39.997 — 7.1 miles : Far side of lake on scree field
  • N40 13.497 W105 40.108 — 7.15 miles : Steep route to right of snow wedge
  • N40 13.499 W105 40.152 — 7.25 miles : Boulder-Grand Pass (12,061')

Camping and Backpacking Information

Backcountry Camping in Rocky Mountain National Park

  • A permit is required for all backcountry camping in Rocky Mountain National Park. Permits may be obtained from the Beaver Meadows Visitors Center Backcountry Office, or the Kawuneeche Visitor Center at Grand Lake. Day-of-trip permits may be obtained in-person, year round.
  • There's a $26 fee to backcountry camp in Rocky Mountain National Park (May 1 - October 31). This administrative fee covers each party (defined as an individual or group) for the duration of the trip. Note that park entrance fees are applied separately and in full.

Backcountry Campsites in the Wild Basin Area

Pine Ridge Backcountry Campsite

  • The Pine Ridge site is located 1.4 miles from Wild Basin Trailhead at 8,880'. There are 2 individual sites and a privy. 2 backcountry sites are located in a lodgepole forest north of the trail, just east of the bridge across North St. Vrain Creek. A food storage cable is about 8 steps past the spur to site #1. It's in a small clearing to the left and runs perpendicular to the trail. Obtain water from North St. Vrain Creek.

Tahosa Backcountry Campsite

  • The Tahosa site is located 1.7 miles from Wild Basin Trailhead at 9,040'. There is 1 individual site and no privy. The site is .3 miles up the unimproved backcountry campsite access trail in a lodgepole stand at the edge of a small rocky bluff. Obtain water from N. St. Vrain Creek, approx. 160 yards downhill from the site.

Aspen Knoll Backcountry Campsite

  • The Aspen Knoll site is located 2.0 miles from Wild Basin Trailhead at 9,400'. There is 1 individual site and no privy. The site is located along the unimproved backcountry campsite access trail in a mixed aspen-pine forest. Obtain water from North St. Vrain Creek, approximately 200 yards downhill from the site.

Siskin Backcountry Campsite

  • The Siskin site is located 3.2 miles from Wild Basin Trailhead at 9,460'. There is 1 individual site and no privy. The site is located along the unimproved, backcountry campsite access trail in a lodgepole stand. Obtain water from North St. Vrain Creek, approx. 135 yards downhill from the site.

North St Vrain Backcountry Campsite

  • The N. St Vrain site is located 2.65 miles from Wild Basin Trailhead at 9,560'. There are 2 individual sites and a privy. The sites are located along the unimproved backcountry campsite access trail, right where it rejoins the main trail. A food storage cable is located 20 steps up the access trail in a small clearing on the left, and parallel to the trail. The sites lie in a thick lodgepole stand on the north side of the trail, just after it crosses N. St. Vrain Creek. Obtain water from the creek.

Thunder Lake Backcountry Campsite

  • The Thunder Lake site is located 6.8 miles from the Wild Basin Trailhead at 10,574'. There are 3 individual sites, 1 group site and 1 stock site. The individual sites are located in a forested area north of the trail about 300 yards east of the lake. The stock site is about 100 yards from the lake on the south side of the trail and slightly east of the hitchrack. Obtain water from Thunder Lake's outlet stream.

Fishing Information

A valid Colorado fishing license is required for all persons 16 years of age or older to fish in Rocky Mountain National Park. No other permit is necessary; however, special regulations exist. It's your responsibility to know and obey them. 

Due to the dynamic nature of fisheries management, fishing regulations can change at anytime. Special closures may be put in place above and beyond what is listed here. Contact the park before heading out for current information.

  • Method of Capture: Each person shall use only one hand-held rod or line. A 'second rod stamp' is not honored in park waters. Only artificial lures or flies with one (single, double, or treble) hook with a common shank may be used. "Artificial flies or lures" means devices made entirely of, or a combination of, materials such as wood, plastic, glass, hair, metal, feathers, or fiber, designed to attract fish.
  • This does not include: (a) any hand malleable material designed to attract fish by the sense of taste or smell; (b) any device to which scents or smell attractants have been externally applied; (c) molded plastic devices less than one and one-half inch in length; (d) foods; (e) traditional organic baits such as worms, grubs, crickets, leeches, minnows, and fish eggs; and (f) manufactured baits such as imitation fish eggs, dough baits, or stink baits. Fly fishers may utilize a two hook system, where one hook is used as an attractant.
  • While in possession of any fishing equipment, bait for fishing (insects, fish eggs, minnows, or other organic matter) or worms is prohibited. Children 12 years of age or under, however, may use worms or preserved fish eggs in all park waters open to fishing except those designated as catch-and release areas.
  • No bait or worms are allowed in catch-and-release waters.
  • Use of lead sinkers (or other lead fishing materials) is strongly discouraged.

Rules and Regulations

  • A $20 Day Use Fee is required to enter Rocky Mountain National Park (or $30 for a 7 Day Pass).
  • Dogs are not permitted on hiking trails in Rocky Mountain National Park.

Directions to Trailhead

Thunder Lake and Boulder-Grand Pass are accessed from the Wild Basin Trailhead in Rocky Mountain National Park. The trailhead is located 2.3 miles west of Highway 7 between the towns of Allenspark and Estes Park.

From Estes Park, head south on Highway 7 for 11 miles to the Wild Basin turnoff on the west side of the road. Turn west on the dirt road to the entrance station .15 miles ahead. The Wild Basin Trailhead is located 2.15 miles from the entrance station. Parking is limited, and roadside restrictions are strictly enforced.

Contact Information

Rocky Mountain National Park
Visitor Information:

Backcountry Office:

Campground Reservations:

Trip Reports

There are no trip reports on this trail.


"It's so worth going past Thunder lake to the pass. It's hard (1500' up per the article) but the views and open alpine is totally worth it. Lake of Many Winds is also really nice, so don't worry if you can't make it all the way up. Thunder gets crowded but you won't find too many people heading up this way - and it gets really nice shortly past thunder above treeline. One word of caution - terrain is really unstable on that final push. You won't fall, but rocks will. Definitely keep lots of space between people."
Tess Bulger  -  Denver  -  Date Posted: August 23, 2017


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