Butte's Southwest Neighborhood is a large residential neighborhood spanning Missoula Gulch, and occupying the southwestern-most corner of the Butte-Anaconda Historic District. The oldest settled portion of Southwest Butte lies east of Missoula Gulch, within the Original Townsite, where residences date to the late nineteenth and first decade of the twentieth century. However, neighborhood development took off between 1912 and 1920, during Butte's 1910s "building boom." Since the area's original platting. Southwest Butte has emerged as a middle-class neighborhood without clear ethnic associations.