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MONTANA 4x4 TRAIL GUIDE · MT-0015

Thompson Lake

Maxville · Boulder Creek · Flint Creek Range, Montana
5/10AGF Difficulty · Moderate
OUT & BACK6.7-mile core trail (onX)
ROCKYLedges near the lake
USFSPintler Ranger District (verify)
LEGAL ACCESS TO THE LAKE IS UNCONFIRMED. No official map of motorized routes covers this area online, and the Forest Service road data AGF found ends about 1.4–1.8 miles short of the lake. Before you drive the last stretch, confirm with the Pintler Ranger District (406-859-3211) that it is open to your vehicle; if it is not, stop where the motorized route ends. Lower Boulder Creek and the Princeton townsite include private homes and likely private mining ground: stay on the road and respect posted and gated land. Stay out of the old mine workings near the lake. Read Know Before You Go.
WHAT THIS GUIDE COVERS

Maxville to Thompson Lake

From Maxville up the Boulder Creek drainage past Princeton to Thompson Lake, the route of AGF's Aug. 9, 2025 40s Only run (about 18 miles one way including the approach, per the club's planning thread).

NOT INCLUDED: the Goat Mountain Lakes continuation (no source found for its motorized status) and any side routes.
WHY 5/10

Moderate · Rock Ledges

AGF rates a trail by its hardest unavoidable obstacle in normal dry conditions. onX describes a very rocky, narrow trail with water crossings, getting steeper with rock ledges near the lake. onX recommends 33-inch tires, at least one locker and sliders. Snow and runoff make it harder.

Rock
4/5
Mud
2/5
Water
2/5
Exposure
3/5
Snow
4/5
Pinstriping
4/5

Snow, mud, runoff, deadfall and fire are condition changes, not part of the base rating.

ROUTE & MAP

Getting There

Maxville is on MT-1, about 11 miles north of Philipsburg. Secondary sources: head east from Maxville on Maxville Road up Boulder Creek about 6 miles to the Princeton townsite. The route from Princeton to the lake is not confirmed by any official source; confirm it with the Pintler Ranger District. Note that the "Boulder Creek Trailhead" listed online near Darby and Forest Trail 8036 are different routes.

LOADING MAP…
Beaverhead-Deerlodge alerts →ROUTE FILE: not published yet

The pin marks Thompson Lake (USGS GNIS 792095). Montana has several Thompson Lakes; this is the Granite County lake near Maxville. No downloadable track is published.

VEHICLE FIT

Rig Requirements

Stock 4x4
Limited — stock 40s ran historically, but current trail reports favor modification
High clearance
Yes
Tires
33-inch recommended
Rear locker
Recommended
Front locker
No
Winch
Recommended
Full-size
No — full-size not recommended
Body damage
Moderate risk

Short, narrow rigs are best. Plan on 33-inch tires, sliders, at least one locker and recovery gear. Full-size rigs may need spotting and should accept body-damage risk.

TRIP PLANNING

Know Before You Go

Season
Summer through fall; no official dates found, verify
Typical trip
Full day from Maxville; 2–4 hours on the core trail
Camping
Lake camping reported; verify current rules
Trailer parking
Philipsburg staging; verify trailhead parking
Turnaround
Limited
  • A food storage order applies Mar. 1–Dec. 1 on the Beaverhead-Deerlodge.
  • Hay, straw or mulch must be certified weed-free (order R1-2025-01).
  • No 2026 condition report was found; the last known run is AGF's Aug. 9, 2025 club run.
SOURCES

Sources & Review

Last reviewed Oct. 8, 2026. No closure found. Whether motor vehicles may legally reach the lake is unconfirmed (see the warning above). AGF last drove it on Aug. 9, 2025.

AGF ratings describe normal, dry-condition difficulty. They do not mean a route is legal, open or passable today. Spot something out of date? Use the Contact page.