Montana · Area of Critical Environmental Concern
Acid Shale-Pine Forest
BLM's map records no relevance finding for this one. BLM's records place no claim, lease or right of way inside the line today, and six grazing allotments cover part of it. It covers 2,674 acres and was designated July 30, 2020, in the Lewistown RMP 2020. In the plan's name, RMP stands for resource management plan.
One of the 1,120 places the Bureau of Land Management has designated an Area of Critical Environmental Concern. This page shows its line, what BLM found there and what sits inside it.
The line
Ground: USGS The National Map, topographic tiles. Boundaries: BLM's own, read Oct 20, 2026. The 6 grazing allotments below aren't marked.Grazing allotments
6 grazing allotments cover part of this line. Their permittees aren't named here yet.
- BASSETT PLACE7,706acres
- WILLIAM LEWIS INDIVIDUAL5,031acres
- WALKER RANCH A,B,D4,262acres
- FORD CREEK4,177acres
- WARHORSE INDIVIDUAL1,069acres
- WEST BASSETT328acres
The nearest areas
- Stark SiteMontana/Dakotas · 799 acres · 3 grazing allotments covering part of it43miles
- Cow CreekMontana/Dakotas · 19,414 acres · 6 grazing allotments covering part of it54miles
- Azure CaveMontana/Dakotas · 143 acres · a grazing allotment covering part of it55miles
- Zortman/Landusky Mine ReclamationMontana/Dakotas · 2,686 acres · at least 4 active mining claims, 17 rights of way, 2 grazing allotments covering part of it57miles
- Castle ButteMontana/Dakotas · 184 acres · a grazing allotment covering part of it75miles
More from BLM's Montana/Dakotas office
Every area BLM's Montana/Dakotas office holdsThe proposed rule
A proposed rule, RIN 1004-AF53, would change how BLM drafts every land use plan, and how it designates ACECs like Acid Shale-Pine Forest. The comment window hasn't opened: the proposed rule wasn't in the Federal Register at our last check. The Watch sends one email the day it prints.
The rule's abstract
The purpose of this rulemaking is to establish in regulations an updated process for the approval of the development, revision, amendment, and maintenance of land use plans, as provided for by the Federal Land Policy and Management Act of 1976, for public lands administered by the Bureau of Land Management (BLM). Additionally, this rulemaking will provide clarification of the process the BLM uses for designating Areas of Critical Environmental Concern.Unified Agenda entry for RIN 1004-AF53, Publication ID 2026, reginfo.gov (OMB OIRA), read Oct 18, 2026