The St. Louis - San Francisco Railway bought a total of thirty 4-8-2s from the Baldwin Locomotive Works to be used in passenger service. Fifteen (road numbers 1500 through 1514) were delivered in 1923, five (road numbers 1515 through 1519) came in 1925 and the final ten (road numbers 1520 through 1529) arrived in 1926.

All thirty of these "Mountains" had 28 x 28 cylinders, 69" drivers, a 210 psi boiler pressure, a tractive effort of 56,800 lbs and total locomotive weight as shown in the chart below.

During the late 1930s, the SLSF needed new locomotives, and money was tight, so the West Springfield Shops undertook a project to build a total of 34 4-8-2s from older locomotives. The first eleven of these rebuilds, outshopped in 1936 and 1937, were built from used 2-10-2 parts and were assigned road numbers 4300 through 4310. They had 27 x 30 cylinder, 70" drivers, a boiler pressure of 250 psi, a tractive effort of 66,400 lbs and weighed 431,110 pounds.

Another 23 4-8-2s were built using the boilers from 2-10-2s between 1939 and 1942. These locomotives were assigned road numbers 4400 through 4422 and had 29 x 32 cylinders, 70" drivers, a boiler pressure of 210 psi, a tractive effort of 68,600 lbs and weighed a whopping 449,760 pounds. They were the heaviest Mountains ever built. Locomotives numbers 4400 through 4412 were built as oil burners and numbers 4413 through 4422 burned coal.

There are six surviving SLSF "Mountains".

• 1501 at a city park in Rolla, MO
• 1519 at the Railroad Museum of Northwest Oklahoma in Enid, OK
• 1522 at the Museum of Transportation in St. Louis, MO
• 1526 at the Museum of the Great Plains in Lawton, OK
• 1527 at Spring Hill Park in Mobile, AL
• 1529 at Frisco Park in Amory, MS

Number 1522 was donated to the Museum of Transportation in the early 1950s. It was restored to operating condition by a volunteer group known as the St. Louis Steam Train Association and has run several excursions. Today, it is undergoing a major overhaul and is scheduled to run again in May of 1999.

Class 4300 (Locobase 8652)

Data from 1947 and 1951 St L-SF locomotive diagram books supplied in May 2005 from the extensive collection of Allen Stanley.

Jim Quarles in a 1996 article entitled "Those Magnificent, Distinctive, Homebuilt, Frisco Mountains" (published on the web at http://home.mchsi.com/~zquarles/friscomountains.htm, accessed 7 July 2007) says that this set of 11 engines was used to test the idea of rebuilding the never-satisfactory 2-10-2s into dual-service Mountains.(The more definitive conversions of 1939 -- the 4400 class -- are discussed in Locobase 224). 4300s used a cast frame and rode on Scullin disk drivers. Thermic syphons enriched the firebox heating surface in both the firebox itself and the combustion chamber. 14" piston valves admitted the steam to the cylinders.

According to Quarles, "They did have problems with the boilers cracking, because of a deficiency of the type of material specified for use in the boilers." He adds in the shops' defense: "Remember much of the advancements in metallurgy and technology during this period was being done by the railroads. The stresses and strains a boiler goes through are not trivial."

The Frisco nevertheless secured 15 years of useful work before dieselization rendered them redundant. The class was "dismissed from service" between 23 April 1952 and 20 October 1952.

Class 4400 (Locobase 224)

Data from 1947 and 1951 St L-SF locomotive diagram books supplied in May 2005 from the extensive collection of Allen Stanley.

Frisco rebuilds reusing all parts of earlier 2-10-2s (Locobase 8537) above the running gear. Oil-burners 4400-4412 pulled both freight and passenger trains; 4413-4422 burned coal and pulled freights only. Jim Quarles in a 1996 article entitled "Those Magnificent, Distinctive, Homebuilt, Frisco Mountains" (published on the web at http://home.mchsi.com/~zquarles/friscomountains.htm, accessed 7 July 2007) argues that about all that was left of the 2-10-2 in the conversion was the original builder's plate.

The St Louis-San Francisco's 1947 locomotive diagram book shows that the firebox had 2 Nicholson thermic syphons of 76.2 sq ft in area and that the piston valves measured 15" in diameter. It also shows that 4407 & 4409 weighed considerably less on the drivers (278,850 lb). (Indeed, 4405-4409 had less superheating surface, their boilers holding only 54 flues but 245 tubes.)

The increases in heating surface and larger piston valves, together with the greater cylinder volume, made for more power at speed than the first set of conversions (see Locobase 8653 for the 4300s.)

Class T-54 (Locobase 223)

Data from table and diagram in 1930 Locomotive Cyclopedia and SL&SF 1930 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. Works numbers were 56137 in January 1923; 56265-56278 in March; 58606-58610 in August 1925; 59132-59134, 59169 in April 1926; 59198-59203 in May.

Firebox fitted with combustion chamber and thermic syphons. The boiler and firebox were very similar in size to that of Frisco 2-8-2s delivered by Baldwin in the same period. 1500-1514 burned oil fuel and used Baker valve gear. Problems with the Baker gear (which were later cleared up, according to Don Wirth in January 1989 Railfan), led the Frisco to order the next five with Walschaerts gear in 1925 followed by the last 10, also with Walschaerts gear, 1926. Wirth notes that although these 10 were delivered with Sellers injectors and were coal burners, but were shortly converted to oil firing with Chicago injectors.

"Throughout their careers,"says Wirth, "...the 1500s were well liked by engine crews, dispatchers, and the motive power department. They were a true general-purpose locomotive, as well suited for use in hotshot freight service, fast passenger service, or even on the local." Some of their passenger runs were impressively long and included St Louis to Oklahoma City (542 miles) and Kansas City to Birmingham (737 miles) without engine change.

The diagram for 1522, in the last batch delivered by Baldwin in 1926 and which has been preserved, shows slightly different heating surface numbers. They are:

Firebox: 411 sq ft

Total EHS: 4,432 sq ft

SHS: 1,222 sq ft.

Weights are a little higher as well: 248,520 lb on the drivers, 360,590 lb total engine weight.