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MONTANA 4x4 TRAIL GUIDE · MT-0031

Frohner Meadows Road (FS 1878) — Lava Mountain Area

FS 1878 from the FS 4009 junction · Helena Ranger District · near Clancy, Montana
NOT RATEDVerify: no source describes FS 1878's obstacles
TRAIL #244: NO FULL-SIZEWheeled OHVs 50 in. or less only; not covered by this guide (MVUM)
HIGHWAY-LEGAL ONLYFS 1878 beyond MP 2.97 and the FS 4009 approach (MVUM)
USFSHelena-Lewis and Clark NF · Helena RD
LAVA MOUNTAIN TRAIL #244, AND AGF'S EARLIER LAVA MOUNTAIN LOOP THAT USES IT, ARE NOT OPEN TO FULL-SIZE VEHICLES. THIS GUIDE DOES NOT COVER THEM: DO NOT DRIVE TRAIL #244 IN A FULL-SIZE RIG. FS 1878 BEYOND MP 2.97 IS OPEN TO HIGHWAY-LEGAL VEHICLES ONLY: NO UNPLATED ATVS OR UTVS. The Forest Service's live MVUM data lists Trail #244 Lava Mountain (MP 0–3.317, Helena Ranger District) as "Wheeled OHV <50", Seasonal": open only to ATVs, motorcycles and other wheeled OHVs 50 inches wide or less, Dec. 2–Oct. 14, and closed to all motor vehicles Oct. 15–Dec. 1. The Forest Service trail inventory marks four-wheel-drive vehicles as restricted on Trail #244 all year. Frohner Meadows Road (FS 1878) is "Roads open to all Vehicles, Yearlong" from MP 0 to 2.907 and "Roads open to highway legal vehicles only, Yearlong" from MP 2.97 to 5.629 (live MVUM data). MP 2.907–2.97 has no MVUM row: verify before you drive past MP 2.907. The approach, FS 4009 Park Lake from its east end to the FS 1878 junction, is "Roads open to highway legal vehicles only, Yearlong" (live MVUM data). Park Lake: Order 01-15-12-26-02 closes all National Forest System lands in the immediate area of Park Lake and FS 4009 in its entirety beginning at its intersection with FS 1878 (the road into the Park Lake campground and day-use area), June 1, 2026 through Oct. 31, 2027, for dam construction. Turn onto FS 1878 at the junction, and do not stop or walk toward the lake where FS 1878 passes about 0.4 mile west of it (AGF calculation from MVUM geometry); obey posted closure boundaries. FS 1878-D1 Frohner Stub is open to all vehicles Dec. 2–Oct. 14 only (live MVUM data). How you reach FS 4009 from Clancy, and the land status of that approach: verify. Confirm the 2026 MVUM with the Helena Ranger District (406-449-5201). Official closures, posted signs and private property override this guide. Read Know Before You Go.
NO RECORD OF AGF DRIVING FROHNER MEADOWS ROAD. NOT RATED: NO SOURCE DESCRIBES FS 1878'S OBSTACLES. No record of AGF driving this route (AGF Verified: NO), and no AGF track or photo album was recovered. AGF's earlier 5/10 described the Lava Mountain loop, which full-size vehicles may not drive; it does not apply to this road. Everything here comes from official sources, plus clearly labeled secondary sources.
WHAT THIS GUIDE COVERS

Frohner Meadows Road (FS 1878) for Full-Size Vehicles

FS 4009 Park Lake from its east end (about 46.4602, -112.1057) to the FS 1878 junction (about 46.4578, -112.1680), then FS 1878 Frohner Meadows south to MP 2.907 (about 46.4286, -112.1903; all vehicles). FS 1878 continues from MP 2.97 to its end at MP 5.629 (about 46.4115, -112.1474; highway-legal vehicles only), but the short link between MP 2.907 and MP 2.97, where Trail #244 also meets the road, is in neither the MVUM nor the Forest Service road inventory: do not continue past MP 2.907 until the Helena Ranger District confirms it is open to your vehicle, and do not turn onto Trail #244. All coordinates are live FS MVUM geometry, not field-checked. Total length of the approach: verify.

NOT INCLUDED: Lava Mountain Trail #244 and any loop that uses it (not open to full-size vehicles), FS 1878 beyond MP 2.907 until the MP 2.907–2.97 link is confirmed, FS 4009 beyond the FS 1878 junction (closed through Oct. 31, 2027), FS 1878-D1, the 26.2-mile onX "Lava Mountain Loop", and side spurs.
NOT YET RATED

Not Rated (Verify)

AGF rates a trail by its hardest unavoidable obstacle in normal dry conditions. No official or secondary source found describes the obstacles on FS 1878 itself, so AGF has not rated it. The MVUM map symbol for both FS 1878 segments and for FS 4009 is "Dirt Road, Suitable for Passenger Car." onX (secondary) says the access road from Clancy "tends to be heavily rutted." The boulder section in onX reports is not placed on FS 1878, and the earlier 5/10 for the loop does not apply here.

Not rated: verify.

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

ROUTE & MAP

Getting There

No official directions were found. FS 1878 begins at its junction with FS 4009 Park Lake, about 46.4578, -112.1680 (live FS MVUM geometry, not field-checked). FS 4009's east end is at about 46.4602, -112.1057. Turn south onto FS 1878 at the junction: FS 4009 beyond it, to Park Lake, is closed through Oct. 31, 2027. How you reach FS 4009 from Clancy or I-15, and the land status of that approach: verify with the Helena Ranger District (406-449-5201).

LOADING MAP…
HLC NF alerts →Park Lake closure →ROUTE FILE: not published yet

The pin marks FS 1878 MP 0, its junction with FS 4009 (live FS MVUM geometry; not field-checked). The all-vehicle section ends at MP 2.907, about 46.4286, -112.1903, where Trail #244 also ends: do not take Trail #244 in a full-size vehicle. Past MP 2.907, confirm the MP 2.907–2.97 link with the Helena Ranger District before you continue. No downloadable track is published: AGF has no track for this route.

VEHICLE FIT

Rig Requirements

Not rated: verify.

Full-size
FS 1878 and the FS 4009 approach only (MVUM); NOT Trail #244

Full-size vehicles: FS 1878 and the FS 4009 approach only. Trail #244 is for wheeled OHVs 50 inches or less, and the Forest Service restricts 4WD on it. FS 1878 beyond MP 2.97 and FS 4009 are highway-legal only. Unplated ATVs and UTVs may use FS 1878 MP 0–2.907 but cannot legally reach it on FS 4009 (highway-legal only). Rig guidance for FS 1878: verify.

TRIP PLANNING

Know Before You Go

Season
No MVUM seasonal date: FS 1878 and FS 4009 to the junction yearlong (live MVUM); FS 1878-D1 Dec. 2–Oct. 14; snow: verify
Typical trip
Verify
Camping
Verify; Park Lake campground closed through Oct. 31, 2027
Trailer parking
Verify
Turnaround
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).
  • The HLC alerts page listed no Lava Mountain, Frohner or Clancy alert on Oct. 15, 2026 (fire danger Moderate). Recheck before you go.
  • Contacts: Helena Ranger District (406-449-5201) (FS 1878 MP 2.907–2.97, the approach from Clancy, the 2026 MVUM).
SOURCES

Sources & Review

  • FS EDW MVUM roads (live) (official; single-ID queries Oct. 15, 2026: FS 1878 FROHNER MEADOWS MP 0–2.907 all vehicles yearlong, MP 2.97–5.629 highway-legal only yearlong, both "Dirt Road, Suitable for Passenger Car"; FS 4009 PARK LAKE MP 0–6.077 highway-legal only yearlong; 1878-D1 all vehicles 12/02–10/14; Helena RD)
  • FS EDW MVUM trails (live) (official; id 244 LAVA MOUNTAIN, MP 0–3.317, "Wheeled OHV <50", Seasonal"; ATV, motorcycle and other wheeled OHV open 12/02–10/14; read Oct. 15, 2026)
  • FS EDW TrailNFSPublish (official; trail 244 LAVA MOUNTAIN (011512): 4WD restricted 01/01–12/31; read Oct. 15, 2026)
  • HLC NF: Park Lake closure (Order 01-15-12-26-02) (official; closes "all National Forest System (NFS) lands in the immediate area of Park Lake" and FS 4009 "in its entirety beginning at the intersection of Forest Road 1878," June 1, 2026–Oct. 31, 2027; read Oct. 15, 2026)
  • HLC NF alerts (read Oct. 15, 2026; fire danger Moderate)
  • onX Offroad: Lava Mountain Loop (secondary (crowd); 26.2-mi loop (not this guide's scope); Clancy access road "heavily rutted")
  • 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. Rescoped to Frohner Meadows Road (FS 1878) for full-size vehicles. Lava Mountain Trail #244 is for wheeled OHVs 50 inches or less (Dec. 2–Oct. 14) and is not covered. Not rated: no source describes FS 1878's obstacles. There is no record of AGF driving this route.

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.