Ada County is named for Ada Riggs, who was the first child born in the area and the daughter of H C Riggs, one of the founders of Boise.
Surrounding County Courthouses:
N – Gem County and Boise County
E – Elmore County
S – Elmore County and Owyhee County
W – Owyhee County and Canyon County
Created: December 22, 1864 
County Seat:
Boise 1864 – present
County Courthouse – Boise
Location: 200 West Front Street / South 3rd Street
Built: 2000 – 2002
Style: Modern
Architect: Lombard-Conrad Architects and HDR Architects
Contractor: Morrison Knudsen
Description: The building faces south and is a five story concrete and glass structure. The building is located on landscaped grounds on the east side of the center of Boise. The south front is concave and gas has a cream colored center section with a two story glass walled entrance hall. Above, the building is recessed. Other sections of the building are tired with the north section having glass panels at each corner. The roof line is flat. The building houses the County District Court and County Magistrate Court of the 4th Judicial District.
Old County Courthouse – Boise
Location: 514 West Jefferson Street / 6th Street
Built: 1938 – 1939
Style: Art Deco
Architect: Tourtelette & Hummel and Wayland & Fennet
Contractor: J O Jordan & Son and Jordan Wilcomb.
Description: The building faces south and is a nine story Indiana limestone structure. The building is located on spacious landscaped grounds in the center of Boise. The base is three stories high and the central tower is nine stories. The interior has Art Deco ornamentation and murals painted by Ivan Bartlettin a vernacular style which depict the history of the Western Expansion into Idaho and are perfect examples of the depression-era frugality seen across the nation at the time. The building was a Works Progress Administration project. The building has been purchased by the State of Idaho. The building was purchased by the State of Idaho for use as legislative offices and the building was renovated. The architect is LKV Architects ( Leatham Krohn Van Ocker ).
Note: The interior is simple, architecturally, but the building’s greatest asset is inside. A three floor mural was integrated into the building, because the Works Projects Administration (WPA) was as eager to hire construction workers as artists. Originally designed with each panel representing a legend in Idaho history, the artists (predominantly from outside of Idaho) painted stereotypical western farm scenes.
See: The 4th Judicial District includes Boise County, Elmore County and Valley County.
History: The county was created in 1864 and Bose was selected as the county seat. The county used rented premises. The first courthouse was a three story structure designed by Charles Ostner and built by G W Babcock in 1882. An addition was constructed in 1909. The second courthouse was constructed in 1938 to 1939 and is still standing. The third and present courthouse was constructed in 2000 to 2002 at a cost of $47,000,000.
See: The Idaho Supreme Court is located in the county.
County Courthouse – Boise
Old County Courthouse – Boise
Photos taken 1996, 2004 and 2015