Wild Basin - East Inlet Thru Hike, Wild Basin Trailhead, Rocky Mountain National Park, Colorado

Wild Basin - East Inlet Thru Hike - 16.9 miles

Wild Basin Trailhead

Fourth Lake, Spirit Lake and Lake Verna on the descent from Boulder-Grand Pass

Fourth Lake, Spirit Lake and Lake Verna on the descent from Boulder-Grand Pass

Round-Trip Length: 16.9 miles (distance and elevation gains will vary by route)
Start-End Elevation: 8,510' - 8,391' (12,061' max elevation @ Boulder-Grand Pass)
Elevation Change: +3,551' net elevation gain (4,415' total elevation gain)
Skill Level: Strenuous
Dogs Allowed: No
Bikes Allowed: No
Horses Allowed: No
Related Trails:

Wild Basin - East Inlet Thru Hike - 16.9 Miles Round-Trip

Boulder-Grand Pass connects the Wild Basin Area (east) and East Inlet Valley (west) on a challenging 16.9-mile thru-hike across Rocky Mountain National Park. This feature-filled route includes 6 lakes and lengthy sections of off-trail and unimproved travel.

Trail Map | Photo Gallery

The east-west route begins at Wild Basin and runs 5.8 miles to Thunder Lake, where an unmaintained but well-formed trail continues 1.45 miles to Boulder Grand Pass on the Continental Divide.

Trail-less cross-country travel drops 1.2 miles (west) from the pass across stunning alpine meadows through treeline to Fourth Lake, where you'll pick up an unimproved trail for 1.6 miles to Lake Verna.

The East Inlet Trail runs 6.9 miles from Verna to the East Inlet Trailhead in Grand Lake to complete the thru-hike.

Though long with strenuous and time-consuming sections at high elevation, the Wild Basin - East Inlet Thru Hike is achievable in a day for strong hikers with efficient routing. Get an early start and familiarize yourself with the route before setting out.

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 - valuable time when trying to outpace afternoon storms. Rain can make the pass climb and off-trail descent to Fourth Lake especially difficult, if not treacherous.


  • Wild Basin to Thunder Lake (5.8 miles : 2064' elevation gain)
  • Thunder Lake to Boulder-Grand Pass (1.45 miles : 1487' elevation gain)
  • Boulder Grand Pass to Fourth Lake (1.2 miles : 1701' elevation loss)
  • Fourth Lake to East Inlet Trailhead (8.5 miles : 1969' elevation loss)

Distances will vary by individual route, especially between the pass and Fourth Lake.


The trail rises steadily beside North St Vrain Creek 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 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 shore to a bridge over the inlet (6.05 miles and weaves through treeline into 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').

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 fades here; improvise (right) around LoMW into a large talus field on the west side.

Scramble through the rock to reach scree and loose dirt on the far side of the lake where you'll find 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'). Cross-country travel begins here.


Stay north in the saddle and continue west across broad, sloping meadows to great views over Fourth, Spirit and Verna. The general route to Fourth Lake is clear but specifics - especially through treeline - are not. 

Take advantage of long alpine meadows on the north side of the valley and descend to treeline (8.15 miles : 10,900'). The forest quickly reconstitutes and travel slows through very steep, cluttered timber with limited down-slope visibility.

Proceed carefully and methodically - you don't want to get hurt on this section.

Grades moderate to the north side of Fourth Lake where you'll intercept an unimproved trail (8.4 miles : 10,360'). Travel eases considerably (or at least comparatively) beyond this point. Fourth Lake occupies a wide, flat basin that's worth exploring.


The unimproved trail shifts and undulates mildly along the outlet stream to the open east end of Spirit Lake (8.95 miles : 10,298'). It continues in similar fashion to the outlet and traces it to the open east end of Lake Verna (9.55 miles : 10,200').

Enjoy flower-filled meadows and thin, beach-like strips along the shore. The unimproved trail continues along the north side of Verna with frequent shifts, undulations and minor obstructions to the west end where you'll see a sign marking the beginning / end of unimproved travel (10.0 miles : 10,200').

The maintained portion of the East Inlet Trail begins here and runs above large pools to an outcrop with great views over Lone Pine Lake (10.9 miles). It winds down across several bridges to the east end of Lone Pine Lake (11.3 miles : 9,885').

The trail drops steadily through a beetle-marred forest with little of note for several miles, save numerous cascades and a few short up-down sections your legs will feel.

The pace quickens through nondescript forest to East Meadow, a large expanse cut by oxbows and frequented by moose and elk. The trail passes a connection for Adams Falls to the East Inlet Trailhead (16.9 miles : 8,391').

Illustration of bighorn sheep

The Afield Rocky Mountain app gives on-the-trail information on plants, geology, turn-by-turn-directions, and more. Install it for your next hike in Rocky Mountain National Park.

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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 12.022 W105 35.293 — 1.35 miles : Backcountry campsite access trail split
  • N40 12.304 W105 36.407 — 2.6 miles : Rejoin main trail; bear right
  • N40 12.773 W105 37.495 — 3.9 miles : Thunder Lake - Lion Lake Trail split
  • 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 13.443 W105 39.460 — 6.55 miles : Top of steep snowfield
  • 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 13.499 W105 40.152 — 7.25 miles : Boulder-Grand Pass (12,061')
  • N40 13.507 W105 40.431 — 7.45 miles : Drop to views over East Inlet
  • N40 13.545 W105 40.789 — 7.95 miles : Drop through alpine meadows
  • N40 13.475 W105 40.910 — 8.15 miles : Cross back through treeline
  • N40 13.327 W105 41.101 — 8.4 miles : Fourth Lake
  • N40 13.433 W105 41.573 — 8.95 miles : Spirit Lake
  • N40 13.518 W105 42.118 — 9.55 miles : Lake Verna
  • N40 13.658 W105 42.652 — 10.0 miles : End of unimproved travel
  • N40 13.905 W105 43.634 — 10.9 miles : Outcrop with view over Lone Pine Lake
  • N40 13.905 W105 43.634 — 11.3 miles : Lone Pine Lake
  • N40 13.566 W105 44.566 — 12.45 miles : Cross bridge over creek
  • N40 14.078 W105 46.112 — 14.55 miles : Lower East Inlet Campsite
  • N40 14.262 W105 47.159 — 15.7 miles : East Meadow Campsite
  • N40 14.358 W105 47.991 — 16.9 miles : East Inlet Trailhead

Worth Noting

  • Travel between Lake of Many Winds and Boulder Grand Pass 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.
  • There are many places to camp along the way, though heavy packs will make the steep pass climb and descent to Fourth Lake even more difficult. Consider completing this route as a day hike, or pack light and efficiently for camping.

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

The Wild Basin 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

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