The addition, the smaller section to the west, housed the First National Bank of Helena for the first several years after its construction. We don't know what became of the bank nor how long it lasted in Philipsburg. It could have failed in 1893, the year of the silver crash. Two other banks, the Philipsburg State Bank and the First State Bank were established shortly after this one. They both failed, the former in 1924 and the latter in 1930.
William Weinstein and Angus McDonald in 1887 financed the construction of a two story brick addition to Weinstein's original building, of which the lower floor was used as a branch bank of the First National Bank of Helena. The iron front for the addition was cast by the Bowen Brothers Foundry in Philipsburg.
From NRHP Nomination Form Item number 8, Page 4
Around the mountain from the mining camp of Cable in 1866 came Polish-born merchant William Weinstein with a wagon-load of goods to sell. He became Philipsburg’s first general merchant, constructing the eastern half of this building in the late 1870s or early 1880s to house his business. Ike Sparey located his restaurant and hotel in the western half, completed circa 1887. The structure has since served as a bank, a mortuary, and since 1950 as mining company offices for the current owner, the Taylor-Knapp Company. Second-story balconies, ornamental brickwork, and battlements complement this well-preserved example of 1880s commercial architecture.
From the NRHP Plaque