Butte became the site of the government's fourth largest immigration office and consequently needed a federal building.

After the building opened, the elaborate courtroom was the site of numerous naturalization ceremonies as thousands of immigrants became citizens.

[3] One of the most dramatic incidents in Butte history occurred in the courtroom on May 21, 1924, during Prohibition, which outlawed the sale, manufacture, or transportation of liquor.

John O'Leary, a convicted bootlegger, began shooting a gun wildly about the crowded courtroom before turning it on himself.

[3] The building is located within an area that was once the core of Butte's bustling business district and is also close to local mining activity.

Architect James Knox Taylor expertly adapted the building design to the sloping terrain.

[3] Constructed between 1903 and 1904, the building is an excellent example of the Renaissance Revival style of architecture, which was popular during the Victorian era.

The first story is faced with pale terra cotta and is topped by a belt course that encircles the building.

Bricks on the second and third stories are laid in a pattern called Flemish bond that consists of alternating headers and stretchers.

[3] The Copper Street lobby, which features marble wainscot, is another important interior space that retains original finishes.

The addition was designed by James A. Wetmore, Acting Supervising Architect of the U.S. Treasury Department at that time.