In the 1906 Great Falls City Directory, an ancestor's residence is listed as "River Bank I n of Montana Brewery". In the 1908 directory, this family's residence is listed as "1st n of Montana Brewery".

I am wondering what "I" (Roman numeral 1) and "1st" are referring to exactly. Does anyone know if, in the early 1900s, houses along the west bank of the Missouri River were numbered?

Any help would be appreciated.