Here's the spec's on the Yellowstone and Big Boy locomotives from my "American Locomotives" book.
For years these Yellowstones were the world's largest locomotives and they still remain near the top in this class. They were designed to haul 4,000-ton trains the 216 miles between Mandan, North Dakota, and Glendive, Montana, up 1.1% grades, which service they have performed most satisfactorily. Some improvements such as the addition of roller bearings have been made and their tractive power as last reported was 145,930 lbs.
Builder - Baldwin Locomotive Works. Cylinders (4) - 26" x 32". Weight, total - 1,125,400 lbs. Steam pressure - 250 lbs. Fuel - 27 tons. Water 21,200 gal. Dia. Drivers - 63" Tractive Effort (orig.) - engine - 140,000 lb. booster - 13,400 lb. R.R. Class - Z5.
72 of these locomotives were built, and were operated by the Northern Pacific, Southern Pacific, Baltimore & Ohio, and the DM & IR (Duluth Missabe & Iron Range).
Union Pacific's "Big Boy" locomotive: These 4000 series locomotives can operate on any part of the system and can do up to 80 mph, but produce maximum power continuously at 70 mph. They were perhaps the Union Pacific's most important factor in their handling of wartime freight, developing 6,000 drawbar horsepower at 45 mph, and each doing the work of two other locomotives on one of the toughest hauling jobs on any American railroad.
Builder - American Locomotive Co. Cylinders (4) - 23 3/4" x 32". Weight, total - 1,208,750 lb. Steam Pressure - 300 lb. Fuel 28 tons. Water - 25,000 gal. dia. Drivers - 68" Tractive Effort - 135,375 lb. R.R. Class - 4000
Attachment photo #1 is a Yellowstone at Proctor, Minnesota. My daughter Patti is standing alongside #225.
Attachment photo #2 is Soo Lines Mikados, No. 1024, on display at Thief River Falls, Minnesota. Locomotive built by ALCO's Dunkirk Works in 1912.
Attachment photo #3 is W.M.S.T.R.'s locomotive #353.