Military

Limestone Hills Training Area

The Montana Army National Guard has trained at Limestone Hills since 1959 under a Special Use Permit from the Bureau of Land Management and special arrangements with the State of Montana and a few private landholders. The site is used for maneuver and live fire training for infantry, armor, artillery, engineer, aviation, and special operations units. Approximately 2,400 hectares (6,000 acres) are closed to the public due to the potential for unexploded ordnance (UXO). The actual area with UXO is much smaller, but the closure was expanded to include all vehicle access points to the area (Youmans 1995).

Limestone Hills Training Area comprises approximately 8,000 hectares (20,00 acres) on the east slopes of the Elkhorn Mountains, about 48 km (30 miles) southeast of Helena, Montana. It is bounded on the east by the Missouri River, and by a series of limestone ridges to the west. The topography varies widely from gently sloping terraces to rugged ridges and draws. Elevation ranges from 1,170 to 1,820 m (3,840 to 6,000 feet).

The training area is aptly named. Pre-Cambrian sea sediments became lithified into rock and were overlain with Flathead sandstone, shales, and limestones. Major compressive tectonic activity in western Montana created a complex series of north and northwest trending folds and faults, including the area of Limestone Hills. Most of the soils are derived from limestone parent material and are strongly calcareous. In general, the soils are shallow (< 50 cm to bedrock), runoff is rapid, and the erosion hazard is severe.

The climate at Limestone Hills is semi-arid, and temperatures tend to be extreme in winter and summer. Temperature data from nearby Townsend shows an average range of -6° C (21° F) in January to 20° C (68° F) in July. Mountains to the west create a 'rain shadow' effect in the Missouri River Valley and Limestone Hills. Annual precipitation varied from 17 to 42 cm (6.7 to 16.3 inches) from 1934 -1995, with May and June normally the wettest months.