Missoula historically has been blessed with an abundance of earth materials suitable for construction, with the exception of cement. Suitable hard rock was in place before glaciation and glacially and fluvially-sorted rock debris in and about the valley run the grain size variation from river-boulders suitable for wall construction to non-expansible clayey silt soils of brick-making quality.
The folks who first settled Missoula during the middle 1860’s chose logs and adobe for building materials. Missoula’s strategic location made it an important trading center by the 1870’s, but during its pre-railroad days, builders had to make due with local building materials. Log buildings soon gave way to more formal frame buildings of sawed lumber. Beginning in 1871 builders began manufacturing brick from local clay deposits for commercial buildings, and by 1872 they began building with local stone.
Missoula’s early builders seldom shaped the stones they gathered. They set the individual blocks in the building walls in a seemingly random way called rubble construction. Actually the builders sorted the blocks and fit them together in a way that gives structural strength to the walls. They commonly reserved the flat sides of individual blocks for the exterior faces of walls. Roughly square blocks were selected for building corners, again for structural strength.
Missoula’s first formal commercial building, the Hammond-Eddy Co. building (1872, now demolished) featured rubble stone walls with a brick facade. The brick facade lent a formal look that could not be achieved with rubble stone.
Missoula’s first major building boom followed the 1883 arrival of the Northern Pacific Railroad. Population growth led not only to greater numbers of buildings but also to bigger buildings. Plentiful, low-cost, local brick became the material of choice for commercial buildings. Missoula’s porous bricks readily absorb water, making them vulnerable to decay. Architects, conscious of this porosity, adapted building designs to protect the bricks from moisture. Protruding eaves and cornices kept rain off building facades and walls. The architects and builders also chose impermeable rubble stone for building foundations, thereby preventing the bricks from sponging up groundwater.
The drive for increasingly stylish buildings in the late 1880’s led stone masons to select individual foundation stones for size, shape, color and texture. Stonecutters began rough-shaping the stones to allow tighter masonry, thereby making the walls more structurally stable as well as more attractive. Squaring the building blocks required great effort, but resulted in the finest masonry. Masonry of squared blocks takes the name 'ashlar,' and Missoula masons built in two dominant ashlar styles. Ashlar blocks of variable sizes set in no particular pattern take the name 'random ashlar' while 'coursed ashlar' refers to ashlar blocks of identical heights set in even horizontal rows.
Besides shaping the individual blocks, the stonecutters also chose a surface treatment for the portion of the block exposed on the outside of the wall. Repeatedly striking the stone surface with a multi-bladed tool called a 'bush hammer' yields a smooth 'axed' surface, while featuring the stone’s natural rough surface yields a “rock-faced” finish. Both of these surface treatments are common in Missoula buildings, and the Higgins Block (210 N. Higgins Ave., 1889-90) exhibits fine examples of both types of these surfaces.
True dimension stone appears to have been utilized only for the construction of major commercial buildings, generally in the period of 1888 through about 1910. Thereafter, dimension stone appears in construction only as the half-story of basement works, such as in Main Hall (1898) / Science Hall (1898), Gymnasium (1901), Craig Hall (1902) and the Old Library Building (now Psychology Department; 1908) at the University of Montana.
Structural steel began appearing Missoula primarily for bridges during the 1880’s, going into some of the buildings by the early 1900’s. Building stone began losing its function as a structural material, but gained new life as a decorative material. A number of early twentieth century buildings, such as the Missoula County Courthouse (200 W. Broadway, 1908-1909), feature ax-surfaced granite basal courses which serve no structural function but clearly enhance the appearance. Similarly, the cobblestones which ornament a number of early twentieth century residences serve little or no structural function. Many early twentieth century brick buildings also feature cut-stone sills, lintels and other ornament.
Trident Portland Cement Co. established a plant near Three Forks and began shipping good quality, low-cost cement to Missoula by 1908. Poured concrete construction as well as cast-concrete blocks and imitation stone products lowered Missoula’s demand for dimension stone after 1910.
The post-World War II building boom brought a renewed interest in stone facades for both commercial and residential buildings. Montana stone contractors quarried flaggy varieties, and stone masons set that stone almost exclusively as random ashlar, flagging or rubble. Currently Montana stone masons follow the same trend.