On July 7, 1863, three days after the establishment of the fort by the United States Army, the first Boise townsite was platted consisting of ten blocks, five on each side of Main Street, extending from what is now called 5th Street to 10th Street. Blocks 5, 6, and 7 of that plat still have the same block numbers in the later and official Boise City Original Townsite Survey and are the three core blocks of the proposed historic district.
The district, as a whole, contains the largest number of historically significant and architecturally important commercial buildings in close proximity in the downtown area. That these buildings have survived and are now attracting investment because of their aesthetic and historic character attests to their cultural and economic value.
The district contains the oldest commercial structure in the city (the Perrault Building dating from 1879). It also has the oldest house in continuous use as a residence (the Cyrus Jacobs House constructed in 1864). Most of the buildings, however, date from the turn of the century and exhibit the design vocabulary current at that time, including various vernacular-commercial styles and Romanesque Revival types.
Following the turn of the century many of the buildings were acquired, or built, by the newly arrived Basques who constitute an important and numerous cultural-ethnic group and who continue their language and social ties to the area with the Basque Center and whose history is related to many other buildings in the district.