Trail of the Trilobites, Bob Marshall Wilderness Complex, Montana

Sierra Club Outings Trip # 13167A, Backpack


  • Search for 500 million-year-old fossils in the Trilobite Range
  • Ascend the rugged Continental Divide
  • Hike through the summer range of elk, mountain goats, bear, bighorn sheep, and moose


  • A professional naturalist on staff
  • All meals throughout the trip
  • Group kitchen and camping gear


DatesAug 24–Sep 1, 2013
Difficulty3 (out of 5)
StaffMelinda Goodwater

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Trip Overview

The Trip

Straddling the Great Bear and Bob Marshall Wildernesses, the jagged reefs of the Trilobite Range and the formidable spire of Pentagon Mountain offer some of the most spectacular scenery in the Bob Marshall Wilderness Complex. Large, grassy meadows provide outstanding views of the surrounding cliffs, pinnacles, and hogbacks while exhibiting a profusion of wildflowers and wildlife. We might see mountain goats clinging to vertical cliffs, bighorn sheep leaping among high peaks, moose watering near alpine ponds, or elk grazing majestically. We'll imagine a time 500 million years ago before these mountains existed when the area was under a sea, home of the prehistoric trilobites whose fossils we’ll be searching for.  A professional naturalist will weave together the rich fabric of the geology, wildlife, and flora present.

Second in popularity of extinct life forms only to dinosaurs, trilobites were prolific in seas worldwide for nearly 300 million years.  Arthropods most similar to lobsters and crabs, their one- to four-inch exoskeletons were finely preserved in limestone rock layers.  Such were the conditions 500 million years ago to embed these creatures in what would become the Trilobite Range within the Bob Marshall Wilderness of the Northern Rockies.  Our goal is to discover some of these fossils on this 51-mile loop around their namesake range and enjoy one of America's most precious natural treasures while we're at it.

The 1.5 million acre Bob Marshall Wilderness Complex has been preserved to nurture an array of plant and animal species.  It is one of the only intact ecosystems that, except for bison, is home to all the species present when Lewis and Clark passed through.  An important biological crossroads in wildlife migration, it's the only location in the 48 contiguous states where wolf, grizzly bear, mountain goat, bighorn sheep, wolverine, elk, moose, and mountain lion populations still occur naturally.  Named for a pioneering environmentalist, the Bob Marshall Wilderness Complex, including the Great Bear and Scapegoat Wildernesses, comprises the crown jewel of the American wilderness system -- a virtual wilderness playground. 

Come explore and revel in the beauty of what is affectionately known to wilderness lovers as "the Bob," but be prepared to experience the reality of true wilderness, as this is no manicured national park. Traveling through the last remnants of primeval North America, we’ll follow forested creek beds to high passes across the rugged Trilobite Range and climb through alpine meadows to the Continental Divide. This combination of a knowledgeable naturalist, spectacular scenery, diverse flora and fauna, fossils, and isolation from major population centers offers an unparalleled opportunity to observe and understand a healthy, intact ecosystem. For the challenge of exploration and the excitement of discovery, join us on this unique adventure to the last best place, a refuge for the soul.


Day 1: We'll have an afternoon arrival at our campground to set up camp, have a trip orientation, weigh our packs and refine our packing, arrange tent-sharing partners, and get to know each other over a potluck dinner salad.

Day 2: We'll drive a short distance to our trailhead along Spotted Bear River at 4,200 feet.  From there we'll gradually ascend 700 feet up the forested river valley and hillsides to camp at Pentagon Cabin (4,900 feet) in 8.8 miles. On the way, we'll pass between aquamarine Blue Lakes, the foaming cataract of Dean Falls, and below Limestone Wall and Peak.

Day 3: This morning we'll follow Pentagon Creek below 8,873-foot Pentagon Mountain, one of the highest peaks in the Wilderness, up to the 7,150-foot alpine pass crossing into the Great Bear Wilderness and the Dolly Varden River Valley, named for the local bull trout. From there we descend to the river and beaver ponds framing the sphinx-like peaks that line the valley.  Camp is at the river in 9 miles. 

Day 4: Today we'll continue down Dolly Varden Creek with views of 8,155-foot Argosy Mountain to the west and the western ridge of the Trilobite Range to the east.  We'll cross the many tributary streams that drain the Trilobites until reaching camp at the junction with the Trilobite Range Trail below Chair Mountain in 7 miles.  Camp is at 5,000 feet.

Day 5: Today we'll begin the climb up the Trilobite Range.  Views of peaks as far as Glacier National Park may be seen in forest openings.  Grassy slopes and expansive meadows dotted with wildflowers alternate with subalpine forest as we approach the massive cliffs of Gable Peaks.  We'll continue climbing along the crest of the range while looking for trilobites. From there we'll cross over to the east side of the range at 7,400 feet and descend to camp at Trilobite Lakes set at the foot of the sheer cliffs of Trilobite Peak at 7,000 feet in 9 miles.

Day 6: We'll have a short day with time to look for mountain goats on Trilobite Peak and enjoy the Trilobite Lakes basin, graced with glacier lilies, beargrass, and buttercups.  We'll continue along the Trilobite Range, still looking for trilobites while climbing up to camp at Dean Lake, located at the base of Pentagon Mountain at 7,400 feet, in 4.5 miles. This is camp for two nights.

Day 7: Today will be a layover day to take in the ragged east face of Pentagon Mountain, search for more trilobites, or climb up to the Continental Divide below 8,412-foot Kevan Mountain.  We can continue to the turquoise gem of Lake Levale, tucked in a barren cirque below shadowy crags that overlook the lake.  The optional hike is 9-10 miles round-trip with a climb of 850 feet.

Day 8: We'll climb up to 7,767-foot Switchback Pass at the southern end of the Trilobite Range with views of looming Table Mountain and the Wall Creek Cliffs to the south.  From there we'll descend to Pentagon Creek to camp once again at Pentagon Cabin in 7 miles.

Day 9: On our last day, we'll follow Spotted Bear River back down to the trailhead in 8.8 miles to complete the loop.  A mid-afternoon arrival is expected.



Getting There

This trip begins at 4:00 p.m. on day one at a campground close to our trailhead;however, you are encouraged to arrive earlier than this. The closest airport is Kalispell, Montana.  You may want to arrive a day early in case of flight delays, for plenty of time to ply the gravel and dirt mountain roads, or to see the iconic wonders of Glacier National Park.  It's nearly 100 miles from Kalispell to our campground, with 65 miles of that on gravel and dirt roads suitable for passenger cars.  Rental car sharing and carpooling are strongly recommended and a future departure bulletin will include detailed driving directions and a roster of participants for arranging rides.  There is no public transportation to this remote trailhead.  Due to the unpredictability of wilderness travel, please make return flight reservations for September 2 or later.

Accommodations and Food

Our campground on day one is included with the trip.  This is a small campground with only a few sites, but has tables, restrooms, and no piped water.  You may want to bring your own drinking water.  Campsites while we're backpacking will be at large in the wilderness.

Our first meal together will be a potluck dinner salad on day one, but all meals after that are included from breakfast on day two through lunch on day nine.  A nutritious, high-energy, non-red meat diet is planned.  Any food allergies or limitations should be indicated to the leader as far in advance as possible.  Although red meat will not be served, there will be chicken and fish on the menu.  Vegetarians can be accommodated, but anyone not eating dairy products should consider another trip.  Trip members will be divided into cook crews to prepare and clean-up meals a couple times during the trip.  Stoves, fuel, and other group commissary equipment will be provided.

Trip Difficulty

This trip is rated 3, which means mostly moderate hiking with a few more strenuous days.  Although not suited for total beginners, strong novices with a couple challenging trips under their belts would be welcome.  Our loop is 51 miles long, divided into 4.5 to 9-mile hiking days with one layover day.  Maximum daily elevation gains will be up to 2,500 feet with an elevation range of 4,000 to 8,000 feet.  Good physical condition is necessary to carry a backpack weighing up to 40 pounds for eight days.  Suggestions for an adequate conditioning routine will be sent in a future bulletin.

Because there's a lot of horse traffic in the Bob, it's been nicknamed the Big Muddy.  Sloshing through mud and climbing over down trees could be involved on sections of trail not regularly maintained.  Bridges are not a common sight on streams in the Bob so wading and wet boots should be expected.  In August, thunderstorms are a regular occurrence and rain that can last all day or even snow can happen at any time.

Equipment and Clothing

A detailed equipment list will be sent to all approved participants, but basically you will need to provide your own personal backpack gear.  This includes a backpack large enough to hold your personal gear plus up to 15 pounds of group commissary gear -- about as much as would fill a paper grocery bag.  Other essentials are a sleeping bag that will keep you warm if the temperature drops to freezing (at least 20 degrees); an ensolite or Thermarest sleeping pad;  good quality, lightweight tent (should be shared); good raingear, including backpack cover (garbage bags are inadequate); enough layers of clothing to keep you comfortable between 30-75 degrees; and medium-weight, waterproofed, well-broken-in, and preferably all-leather hiking boots with lug soles.  Hiking poles are also strongly recommended for rough, steep trails and stream crossings.  You will enjoy the trip more if you keep your personal gear to under 25 pounds -- after all, a pound at the trailhead feels like ten a mile down the trail!  Group cooking and camping gear will be provided.



  • Bob Marshall, Great Bear, and Scapegoat Wilderness Complex Map – U.S. Department of Agriculture/Forest Service, available at
  • USGS 7.5-minute topographical maps: Whitcomb Peak, Bungalow Mountain, Trilobite Peak, Gable Peaks, and Pentagon Mountain, available at


  • Molvar, Erik, Hiking Montana's Bob Marshall Wilderness.
  • Shaw, Richard J. and Danny On, Plants of Waterton-Glacier National Parks and The Northern Rockies.



Rich in natural resources, the Northern Rockies have a long history of resource exploitation. An environmentally unfriendly congress, strong interests in mining and other resource development, and a fiercely independent local population leave us an uphill battle to preserve areas left out of the Bob Marshall Wilderness Complex. The biggest population of large mammals in the lower 48 states makes its home in the Northern Rockies and it’s now known that these species need large tracts of wilderness to migrate and interbreed. The Northern Rockies Prosperity Act seeks to add 500,000 acres to the Bob Marshall Wilderness Complex to fill in obvious gaps and to protect the western and eastern fronts of the Wilderness. We will discuss local issues on this trip as well as the Yellowstone to Yukon proposal, which aims to create a 2,000-mile uninterrupted wildlife corridor along the Continental Divide from Yellowstone National Park to the Yukon in Canada. Our goal is to have you come away from this trip with a love for the area and the drive to urge your legislators to support this act.

You can get more information about the threats to this area and how you can help from the websites listed above.

Sierra Club National Outings is an equal-opportunity provider and will operate under a permit from Lewis & Clark National Forest.



Melinda Goodwater has been leading trips for Sierra Club Outings for 20 years and has over 90 outings under her belt. She quit her full-time job when it got in the way of her trips and has been leading adventures ever since. She leads treks from Nepal to the Rockies and Sierra to the desert southwest. Melinda is a very amateur naturalist and particularly enjoys finding unique places off the beaten track. Along with years of experience leading remote and high-elevation outings, Melinda has training in CPR and is a wilderness first responder with 80 hours of first-aid training. She welcomes you to join her while giving every participant personal attention.

Assistant Leader:

Suzanne Swedo is a botanist who has led wilderness seminars for the Yosemite Conservancy for more than 25 years and is the author of Hiking Yosemite National Park. She leads natural history-oriented outings around the world for other organizations as well as her own adventure travel company. She has led more than 60 Sierra Club National Outings, written a number of other trail guides for Falcon Publishing, and backpacked the mountains of every continent.

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