Industrial Helena Limekilns

The old lime kilns south of the Helena city limits provide a highly visible and picturesque link to the area’s industrial past. Although sometimes misinterpreted as mining (ore) smelters, these brick and mortar kilns were used to manufacture quicklime from native limestone before the turn of the 20th Century. Those near the junction of Grizzly and Orofino Gulches lie on private property but others can be found nearby on National Forest land.

The first Helena lime kilns were built in the early 1870s by Irish immigrant Joseph O’Neill. Wood was the primary building material of early-day Helena until a series of catastrophic fires in the 1870s reduced parts of the city to rubble. Thereafter, stone, brick, mortar and plaster became prominent in home and business construction. The lime kilns were subsequently sold to James Kervin and then to James McKelvey, a former employee of O’Neill. The McKelvey family still owns kiln ruins in Grizzly Gulch just south of Helena.

Helena’s quicklime industry flourished until the early 1900s, when the Elliston Lime Company mine began operations just west of MacDonald Pass. Located adjacent to the Northern Pacific Railroad line, this limestone plant was able to cost-efficiently ship its commercial product to communities throughout Montana. In contrast, the Helena lime plants relied on wagons to haul quicklime to the railhead in Helena. Because of this small but extra step, the Helena lime operations could not financially compete. The Elliston lime plant successfully operated until 1965, when it burned down in a fire.

Limestone was created millions of years ago by sea fossils deposited on the bottom of a now vanished ocean floor. It is a prominent and visually appealing aspect of Helena area geology. Limestone could thus be readily quarried from highly visible outcrops located directly above or nearby the lime kilns. The limestone was removed by drilling, blasting and minor above-ground excavation.

The Helena lime kilns are called continuous kilns. In essence, they are vertical furnaces made of mortar, brick, wire cable and wood poles. The square-shaped kilns had openings at the top and at the base. Alternate layers of wood fuel and quarried limestone cobbles were stacked inside the kiln, and fired at a high temperature. Wood and limestone was continuously fed into the top of the kiln while the resulting and powdery quicklime was shoveled from the bottom kiln mouth into wood barrels. Sheds (which have long since disappeared from the Helena ruins) were attached to the kiln mouths to protect the barrels of raw and volatile quicklime from moisture.

The chemistry of lime-burning process is simple. Limestone is mostly calcium carbonate (CaCO3). When heated at 700 to 900 degrees C (1648 F), it decomposes to yield calcium oxide (CaO) or quicklime and carbon dioxide gas. Historically, kilns were fired for 48 to 72 hours, with additional time allowed for cooling. Too much heat and the lime was “deadburned” and became dense with low porosity or chemical reactivity. Too little heat yielded soft-limestone that has the opposite characteristics. Either situation reduced the commercial value of the rendered quicklime.

Depending on local impurities, quicklime is white, gray or yellowish in color and has a musty odor. It is stable at all temperatures but the addition of water causes a strong heat-producing, chemical reaction. The reaction of quicklime with water is called slaking. Slaked (or hydrated) lime and sand produces mortar, which hardens on evaporation and is thus highly valued for construction.

Quicklime is one of the oldest chemicals used by humans. Archaeologists have discovered that lime (calcium oxide) was used in mortar in ancient Mesopotamia some 4500 years ago. The Romans used it to make hydraulic cement, which could be set under water for construction and repair of seaports and municipal water systems. In the Middle Ages lime was widely used for tanning leather. During the Renaissance, lime was used in farming to reduce soil acidity. By the time of the Industrial Revolution, the most important use of lime was for mortar and plaster for buildings. Artificial hydraulic cement eventually led to the demise of the quicklime industry. Today, lime serves a variety of purposes in agriculture, manufacturing, and industry.

Helena’s impressive historic architecture owes much to the city’s early lime industry. This importance is now recognized by the inclusion of the McKelvey kilns in the National Register of Historic Places.

The Helena lime kilns are far less sturdy and more vulnerable to destruction than they appear. These crumbling historic ruins are in dire need of stabilization, restoration and public interpretation. Stop, appreciate and photograph the kilns, but please do not climb atop or inside them. Remember also that several of the most prominent ruins near the junction of Grizzly and Orofino Gulches are located on private property.