Boise & Arrowrock 2-6-0 "Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 1 (Locobase 15049)

Data from Roy V Wright (Ed.) 1912 Locomotive Cyclopedia of American Practice, Sixth Edition (New York: Simmons-Boardman Publishing Company, 1912), p. 168. See also "The Bureau of Reclamation - A Brief History" at the Bureau's website (

After some debate, Congress authorized the establishment of the United States Reclamation Service in June 1902 to undertake irrigation projects in the West. The agency originally operated within the US Geological Survey but was set off as an independent bureau in 1907. Projects included dams, channels and canals, and other large earth-moving efforts.

One of the USRS's projects was the Boise Project, which irrigated 230,000 acres (359 sq miles/931 sq km) of western Idaho. A major feature of the effort was the Arrowrock Dam, construction of which involved building the 20-mile (32 km) Boise & Arrowrock up to the site. Designated a common carrier, the B&A carried passengers and freight as the first publicly owned railroad in the United States.

As part of the B&A's equipment, this Mogul was purchased new by the USRS along with several passenger coaches. The contract was let on 15 June 1911 and the engine was valued at $10,140. The railroad operated only as long as construction continued, but in that five-year span, says Wikipedia, " [T]he train ran faithfully through the canyon, delivering over 89,500 visitors and crewmen. And during its commission, the Boise & Arrowrock traveled more than 110,000 miles (180,000 km) and carried 14,000,000 tons of freight."

When the Arrowrock Dam was completed in October 1915 (as the then-tallest dam in the world), the B&A's principal demand source dried up and, after a few months of conveying visitors to gaze upon the dam and reservoir, the B&A closed on 11 August 1916.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID15,049
RailroadBoise & Arrowrock
Number in Class1
Road Numbers1
Number Built1
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.50 / 3.81
Engine Wheelbase (ft / m)20.67 / 6.30
Ratio of driving wheelbase to overall engine wheebase 0.60
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)101,000 / 45,813
Engine Weight (lbs / kg)115,000 / 52,163
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)
Tender Water Capacity (gals / ML)
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)56 / 28
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)50 / 1270
Boiler Pressure (psi / kPa)180 / 12.40
High Pressure Cylinders (dia x stroke) (in / mm)18" x 24" / 457x610
Tractive Effort (lbs / kg)23,795 / 10793.24
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.24
Heating Ability
Firebox Area (sq ft / m2)135 / 12.54
Grate Area (sq ft / m2)28.30 / 2.63
Evaporative Heating Surface (sq ft / m2)1639 / 152.27
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)1639 / 152.27
Evaporative Heating Surface/Cylinder Volume231.87
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation5094
Same as above plus superheater percentage5094
Same as above but substitute firebox area for grate area24,300
Power L14910
Power MT321.53