The ten class I-5 Consolidations were delivered by ALCO-Brooks in 1903. For burning anthracite culm they were given a Wootten firebox with an 82 square foot grate and Camelback design. In the 1920s, all were superheated, with one locomotive keeping the cylinder diameter of 20 inches and the remaining getting 21 inch diameter cylinders. The former were designated I-5s while the rest became I-6s. The tender capacity was increased by a ton by installing boards. The last four members of the class remained in service until 1947.

The locomotives later grouped together in the class E-1 were a total of ten Camelback consolidations that the Delaware & Hudson procured in 1898 and 1899 for burning loose anthracite coal. Three were created by rebuilding a 4-4-0 and two 2-6-0. Seven others were newly built by Dickson and initially designated class U-II before becoming class E-1a.

The Wootten firebox already created a grate area of 80.3 square feet. In addition to the direct radiant area of 170 square feet, it contained a further 104 square feet in so-called “water bars”. One example of the class was built as a compound locomotive with comparatively large cylinders with a diameter of 23 and 34 inches. It was later simpled and scrapped along with its E-1 and E-1a class sisters between 1927 and 1928.

For commuter trains, the Lackawanna needed a passenger locomotive that would combine the ability to burn culm, what means waste from anthracite mining, with the simplest possible maintenance and high tractive effort. It received a Wootten firebox, the grate of which was extraordinarily large in relation to the heating surface and, at 87,7 square feet, was probably one of the largest ever on a 4-4-0. This required a two-part Camelback cab. In order to achieve the required traction, the cylinders were dimensioned sufficiently and at the same time a moderately large driving wheel diameter was selected. The construction of the locomotive itself was kept as simple as possible.

Initially they were classified in the class 19C, but soon received new class designations with “G” for the 4-4-0 wheel arrangement. The first three batches consisted of a total of 27 locomotives and were delivered by ALCO-Schenectady between 1901 and 1903. Although they were almost identical in construction, they received the class designations G-2, G-3 and G-4. All other production lots differed in details and became the G-5 to G-9. Of these, 15 were initially delivered by Baldwin in 1904 before ALCO-Schenectady delivered 12 more in 1905 and finally the last 11 in 1910 and 1911.

Two examples of the class G-6 were equipped with superheaters of Cole type ex works and formed the class G-7. Since the lubrication was not easy to implement with this, this type of superheater was soon removed again. Between 1916 and 1921 many of the locomotives were again fitted with a superheater, but this time a Schmidt type. There were again slight differences in these conversions, which was reflected in the addition of an “a” or “b” after the class names. A single locomotive was given cylinders with a diameter of 21 instead of 20 inches, which earned it the different designation G-10b.

Even the saturated version developed a high power compared to other locomotives with the 4-4-0 wheel arrangement and could haul trains with six cars at an average of 40 mph on the existing mountain lines. Nevertheless, they later had to be used for suburban trains, since their tractive power soon no longer met the increased requirements. Ten locomotives were converted to conventional cabs in the 1920s and thus survived somewhat longer than their non-converted sisters. Most were retired just before World War II.

The class E-1 of the Erie Railroad consisted of 29 Atlantic express locomotives built by Baldwin between 1899 and 1901 and rated for speeds of 100 mph. They were Camelback locomotives with a square Wootten firebox measuring 96 by 96 inches.

Propulsion was provided by a Vauclain compound engine, i.e. with high and low pressure cylinders one above the other. A rebuild began as early as 1904, in which the four cylinders were replaced by two cylinders with simple expansion. One also increased the distance between the tube sheets by six inches to increase the heating surface area.

In the early years of the twentieth century, Mallet locomotives served only as an articulated solution for narrow-gauge railways. The L-1 of the Erie Railroad of 1907 was one of the first to show that very large freight locomotives could also be built with the Mallet principle. At the time it was commissioned, it was the largest and most powerful locomotive in the world. Since it was only intended as a pusher locomotive and did not have to reach high speeds, there was no need for leading or trailing axles. Thus, all eight axles were available as adhesive weight. The wheel arrangement was soon called “Angus”.

A Wooten firebox with a grate area of 100 square feet was used to maximize the energy yield from low-grade coal. In order to still ensure a good view for the engineer, the L-1 was built as a camelback engine and thus had the cab above the rearmost axle of the front bogie. It was the only camelback Mallet ever built.

Only three examples were built, which were used on the Delaware and Susquehanna divisions to push trains up a 1.3 percent incline. They were rebuilt to a more conventional form in 1921. The cab was moved to the rear and two carrying axles were added, whereby they now had the wheel arrangement 2-8-8-2.

The Lehigh Valley had the ability to source large quantities of smaller fragments of anthracite coal as residues from the processing operation at less than a dollar a ton. In order to be able to use these as fuel for steam locomotives, the camelback design was used with a very wide firebox, which included a large grate area. From 1904, a larger series of ten-wheelers was produced, which were suitable for use in front of fast freight trains in the lowlands and heavy local trains.

The locomotives were designed so heavy that the axle load was just suitable for high speeds. The large firebox was a slightly modified Wootten type and did not have a combustion chamber. The load on the individual coupled axles was distributed more rear-heavy to get better traction when starting. The initial wheel diameter of 68.5 inches represented a good compromise between higher speeds and a tractive effort of more than 30,000 pounds. 

There were some changes during production, for example the wheel diameter was increased to 69 inches. While the boiler initially had 378 tubes, this number was reduced to 363 from 1907. With the exception of Baldwin's last delivery, all locomotives had Stephenson-type valve gear. Of the last Baldwin engines, eight had Walschaert valve gear and two had Baker-Pilliod valve gear.

Parallel to the five 4-4-0 with the numbers 659 to 663, the Lehigh Valley had five 4-6-0 built by Baldwin in 1895 and gave them the numbers 708 to 712. These were all Camelbacks and were nearly identical apart from the additional driving axle. They were completed by 20 other 4-6-0 with a slightly smaller boiler. The first of those also got a driver diameter of 68 inches, while the other 15 only had 62 inches.

Later when the new class scheme was adopted, they all got the prefix J, what denoted their wheel arrangement. The locomotives with 62 inch drivers were classed into class J-42, while the ones with 68 inches became class J-43. After rebuilds which changed boiler pressure and cylinder size, they were designated classes J-49 to J-52. The last ones were scrapped in 1930.

The Pennsylvania Railroad wanted to accommodate a larger grate area in Atlantic locomotives in order to be able to burn anthracite and fragments thereof. For this purpose, three locomotives were procured on a trial basis, which had a combination of Wootten and Belpaire fireboxes and were designed as Camelbacks. The special shape of the firebox and the combustion chamber resulted in 218 square feet of direct heating surface and a grate surface of nearly 70 square feet. A visual highlight was the common cover of the steam dome and the sandpit, which looked like a huge steam dome. 

The approximately 410-ton express trains between Philadelphia and Atlantic City could be transported over longer sections at an average speed of around 55 mph. With only 260 tons on the hook, an average speed of 70 mph was achieved on the 58 miles long, slightly descending section from Camden to Atlantic City.

Ultimately, however, the PRR was bothered by the fact that the engine driver and the fireman had difficulty communicating. Hundreds of other Atlantics were procured as a result, but all of them with a conventional firebox and cab at the rear end. The three engines were sold to the Long Island Railroad in 1901 and scrapped in 1911.