Bitter Root Town was a planned development in Ravalli County, Montana, designed by Frank Lloyd Wright. Only one building of the town was completed in 1909, and it later burnt down. (Note on spelling: The river and mountains are both called "Bitterroot", one word, but this development was written as two words).

The context behind the planned development of this town involves two threads: the development of the Bitterroot Valley, and the development of Frank Lloyd Wright, now considered to be the United States' premiere architect. The Bitterroot Valley had developed as a supply base, providing food and lumber, to Montana's copper boom, located some distance away, in Butte and Anaconda. Copper Barons like Marcus Daly had built castle-like mansions in the area. Many people believed that the area was going to grow rapidly in population, fueled by apple orchards and tourism from the East. Because of this, Frank Lloyd Wright had built a resort near Darby, Montana. But his next project was more ambitious: designing an entire town, northeast of Stevensville, Montana.

At the time, Frank Lloyd Wright had been practicing architecture for two decades, and had designed dozens of buildings, mostly in Illinois and other parts of the midwest. Most of the buildings at the time were residential homes in prairie home style. His most famous architectural projects, such as The Tokyo Imperial Hotel, Fallingwater, and the Guggenheim Museum, were still in the future. At the time, Frank Lloyd Wright had not really worked in the mountain west, and the Darby Colony and Bitter Root Town would be his first works west of the Continental Divide.

So...beautiful mountain valley on the verge of a tourism and farming boom, genius young architect, ready to revolutionize not just buildings, but urban planning: this looked like it could have been history in the making. But for several reasons, it never materialized. The Bitterroot Valley has a variable climate, and sometimes farming can seem more viable than it is, as it enjoys several warm years. But then after a few consecutive years of 10 month of frost, it seems like a less likely place for large scale commercial agriculture. The apple boom never manifested there. As a tourist destination, it also never developed. At the time, a train journey from Chicago would have taken several days. Even today, with air travel, it is not an easy place to reach. The company went bankrupt after only one building of the town had been completed, and the one building that was finished burned down in 1924. Frank Lloyd Wright would spend most of the teens living in Europe, or dealing with a variety of personal problems. Although he would pioneer even more innovations in architecture, he never truly made another attempt at planning an entire community.

The community was supposed to include homes, a library, a hotel, an opera house, and even, in one envisioning, a small subway system. Today, nothing verified remains of the community apart from a fire hydrant. (a local librarian told me that a Arts & Crafts style home a mile or so south of the site was a Frank Lloyd Wright design, and while this is plausible, it is not verified). It is an interesting thought experiment to think of how much American architecture, planning and even society could have been changed if an example community designed by Frank Lloyd Wright had inspired other people to build other such communities. Perhaps it would have been nothing but an artistic oddity for the rich, or perhaps it would have changed American community design. Now the site of the planned community is just a stretch of road along a highway in Montana, with no markers of its architectural history.

Sources:
https://flwright.org/researchexplore/wrightbuildings/bitterrootinn
http://franklloydwrightsites.com/montana/index.html
http://www.steinerag.com/flw/Artifact%20Pages/PhRtS145.htm#Town
https://goo.gl/maps/PuujV2dezA22 : Google Maps of the approximate location of the town.