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MONTANA 4x4 TRAIL GUIDE · MT-0005

Lower Boulder Lake (FS 1007 and FS 78004)

Tobacco Root Mountains · Butte Ranger District · Madison County, east of Twin Bridges, Montana
3/10AGF Difficulty · Easy · AGF drove it June 24, 2018
~2.9 MIFS 1007 MP 3.93 to the FS 78004 end, one way (AGF estimate from FS data)
APPROACH: VERIFYRoad below FS 1007 MP 3.93 unconfirmed
USFSBeaverhead-Deerlodge NF · Butte RD
THE APPROACH ROAD BELOW FS 1007 IS UNCONFIRMED. AGF'S 2018 TRACK IS A HISTORICAL RECORD, NOT A CURRENT LEGAL ROUTE: FOLLOW THE CURRENT MVUM. In the Forest Service road inventory, FS 1007 begins at MP 3.93 (about 45.618, -112.1525) on National Forest land; the road below that point is not a Forest Service road, and its name, jurisdiction and land status are unverified. Ask the Butte Ranger District (406-494-2147) how to reach it before you go. MVUM: a 2023 copy of the Forest Service MVUM data lists FS 1007 MP 3.93–3.994 as "Roads open to highway legal vehicles only, Yearlong," FS 1007 MP 3.994–7.34 and FS 78004 Lower Boulder Lk (MP 0–1.25) as "Special Designation, Yearlong" (passenger cars, high-clearance vehicles, trucks, ATVs and motorcycles; 2023 MVUM copy; 2026 MVUM: verify). Side-by-sides wider than 50 inches are not listed: verify. Montana FWP describes Lower Boulder Lake as a backcountry lake; the roads end near it, not at the shore. Do not drive off the designated roads. The Forest Service's live MVUM data has no Beaverhead-Deerlodge roads, so confirm the 2026 MVUM with the Butte Ranger District. Routes not shown on the MVUM are closed to motor vehicles. Correction: AGF's earlier listing pointed to Forest Road #676 and Boulder Lakes Trail #8033 on the Pintler Ranger District. Those are in the Flint Creek Range (FS 676 is Finley Basin Road), not this Lower Boulder Lake. The continuation toward Upper Boulder Lake is excluded. Official closures, posted signs and private property override this guide. Read Know Before You Go.
AGF DROVE THIS ROUTE ON JUNE 24, 2018. AGF's track from that day records a 33.3-mile outing into the Lower Boulder basin, approach included. Its high point (about 45.6096, -112.1222) is on FS 1007 beyond the FS 78004 junction, about 0.2 mile from the lake; whether AGF also drove FS 78004 is unknown. The track is AGF's record of the trip; current access in this guide comes from official sources.
WHAT THIS GUIDE COVERS

FS 1007 to Lower Boulder Lake

From FS 1007 MP 3.93, where the Forest Service road begins, east on FS 1007 about 1.6 miles to the FS 78004 junction (near MP 5.55). From there, FS 78004 Lower Boulder Lk (about 1.25 miles) and FS 1007 (to MP 7.34) both pass close to the lake: about 0.1 mile and 0.2 mile from it at their nearest (AGF calculation from Forest Service road geometry and Montana FWP's lake coordinate). AGF's 2018 track reached about 0.2 mile from the lake on FS 1007. About 2.9 miles one way via FS 78004 (AGF estimate from Forest Service data). Drive only on these roads; the lake shore is not a road. The approach below FS 1007 MP 3.93 is not part of the rated route.

NOT INCLUDED: the approach below FS 1007 MP 3.93 (unconfirmed), the Upper Boulder Lake continuation (harder; rate separately), side spurs, and any route not shown open on the current MVUM.
WHY 3/10

Easy · Mild Rocks and Erosion

AGF rates a trail by its hardest unavoidable obstacle in normal dry conditions. AGF drove it in 2018. Route accounts from 2019 and 2022 (AGF research notes) describe the Jeep trail into Lower Boulder Lake as easy, with occasional undercarriage contact, so AGF rates it 3/10: high clearance, no lockers in normal conditions. The continuation toward Upper Boulder Lake is harder and excluded. The Forest Service maintains both FS 1007 and FS 78004 for high-clearance vehicles (maintenance level 2); that is a maintenance standard, not a condition report. No current condition report was found. Snow and runoff are condition changes, not part of the base rating.

Rock
2/5
Mud
1/5
Water
1/5
Exposure
1/5
Snow
3/5
Pinstriping
2/5

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

ROUTE & MAP

Getting There

From Twin Bridges, the road to FS 1007 MP 3.93 (about 45.618, -112.1525) is unconfirmed: verify with the Butte Ranger District (406-494-2147). Census data shows an unnamed four-wheel-drive track reaching the FS 78004 junction area from the west; it is not a legal-status source. From MP 3.93, follow FS 1007 east to the FS 78004 junction (about 45.6143, -112.1291), then FS 78004 to its end (about 45.6028, -112.1325). Coordinates are Forest Service road geometry, not field-checked. Return the same way.

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

The pin marks Lower Boulder Lake (Montana FWP coordinate; not field-checked), about 0.1 mile from FS 78004 (AGF calculation from Forest Service road geometry). No downloadable track is published: AGF's 2018 track has not been matched to the current MVUM.

VEHICLE FIT

Rig Requirements

Stock 4x4
Yes
High clearance
Yes
Tires
Stock
Rear locker
No
Front locker
No
Winch
No
Full-size
Verify
Body damage
Low risk

A stock high-clearance 4x4 is the baseline (AGF record). Lockers and a winch are not baseline in normal conditions. Carry a full-size spare and basic recovery gear.

TRIP PLANNING

Know Before You Go

Season
No MVUM seasonal date on FS 1007 or FS 78004 (yearlong, 2023 MVUM copy); snow limits it, about summer to early fall (AGF record; verify)
Typical trip
Half day (AGF record)
Camping
Verify
Trailer parking
Verify
Turnaround
At the FS 78004 road end; verify
  • Hunting season: Montana's general deer and elk season runs Oct. 24–Nov. 29, 2026 (FWP). Expect hunters, camps and parked vehicles; wear blaze orange outside the vehicle. Archery season runs to Oct. 18. A youth deer hunt runs Oct. 15–16 (FWP).
  • Bear country: the Beaverhead-Deerlodge annual food storage order applies Mar. 1–Dec. 1 on National Forest land. Store food bear-safe.
  • Contacts: Butte Ranger District (406-494-2147) (FS 1007, FS 78004 and the approach road).
SOURCES

Sources & Review

  • FS EDW RoadBasic (live) (official; FS 78004 LOWER BOULDER LK MP 0–1.2493 (ML2, Butte RD 010204, Madison County); FS 1007 MP 3.93–7.3449 (ML2); geometry; read Oct. 15, 2026)
  • FS MVUM roads, 2023 copy (ArcGIS Online) (official data (2023 copy); FS 78004 Special Designation yearlong; FS 1007 MP 3.93–3.994 highway-legal only, MP 3.994–7.3449 Special Designation, yearlong; FS 676 is FINLEY BASIN (Pintler RD); read Oct. 15, 2026)
  • FS EDW Basic Ownership (official; National Forest at FS 1007 MP 3.93 and at the FS 78004 end)
  • Census TIGERweb local roads (federal; unnamed S1500 four-wheel-drive track west of FS 78004; not a legal-status source)
  • Montana FWP: Lower Boulder Lake (fisheries information) (lake coordinate 45.60807, -112.12644; described as a backcountry lake; URL: verify (cited in AGF's decision log, batch 70))
  • Route accounts, 2019 and 2022 (AGF research notes) (internal AGF research (decision log, batch 76); Jeep trail into Lower Boulder Lake described as easy, with occasional undercarriage contact; source URLs: verify)
  • Beaverhead-Deerlodge NF alerts (read Oct. 14, 2026; fire danger Moderate)
  • Beaverhead-Deerlodge NF: Offices (Butte RD, 1820 Meadowlark, Butte, 406-494-2147)
  • Montana FWP: Hunting seasons (2026 deer/elk archery Sept. 5–Oct. 18; youth deer Oct. 15–16; general Oct. 24–Nov. 29)

Last reviewed Oct. 15, 2026. FS 1007 and FS 78004 are on the 2023 MVUM copy, yearlong (2026 MVUM: verify), but the approach below FS 1007 MP 3.93 is unconfirmed. AGF drove this route on June 24, 2018.

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.