The Jackson Block’s spare façade bears witness to those watchwords of modern architecture, “form follows function.” The two-story building suggests ways that urban architectural trends were translated and adapted in small communities. Its main decoration derives from the pattern created by its windows; in this, the 1909 commercial block echoes the emphasis found in turn-of-the-century “Chicago-style” skyscrapers on “light, space, air, and strength” rather than ornamentation. Miles City architect Brynjulf Rivenes designed the surprisingly modern building for entrepreneur W. C. Jackson, a confectioner who owned a shop at 613 Main. With fellow Miles City businessman Ed Arnold, Jackson also invested in the next-door Arnold Block. Built in 1913, it matched the lines of the Jackson Block, and doorways connected the buildings on the second floor. From Jackson Block storefronts merchants sold pianos, office equipment, clothing, and dry goods. Second-floor tenants included Brynjulf Rivenes and the Montana Institute, a private school that offered both day and night classes in automobile engineering, bookkeeping, stenography, and penmanship.