The first British locomotive to run in regular service in this country was the John Bull, imported by the Camden and Amboy in 1831 and later used as the model for Old Ironsides, the locomotive Matthias W. Baldwin built in Philadelphia for the Philadelphia, Germantown and Norristown. The Mohawk and Hudson brought in another John Bull from its namesake country. The latter engine, tested gingerly late in 1831 by the road's chief engineer, John B. Jervis, was deemed too heavy, with its weight of more than six tons, to run safely on M&H tracks, which were made of timber faced with iron. This problem was overcome by substituting a swivel front truck with two axles and four wheels for the rigid front axle with single wheels. The 'bogie-truck' designed by Jervis was an impressive example of the skill and ingenuity of American engineers and mechanics, and U.S.-made locomotives soon outnumbered British - built engines on American railroads.
The chief engineer of the Philadelphia, Germantown and Norristown, Henry R. Campbell, invented the four-coupled locomotive in 1836. Named the Blackhawk, it had the 4-4-0 wheel arrangementa four-wheel leading truck, four driving wheels coupled, and no wheels behind the drivers.
In 1840 the Gowan and Marx, a 12-ton 4-4-0 Philadelphia and Reading locomotive, pulled a train of 101 freight cars almost 40 times its weight at a speed of ten miles an hour. In the same year, Matthias W. Baldwin developed a special steam-tight joint which permitted 120 pounds of pressure in his engines. He also began experimenting with coal as fuel and started to investigate the possibility of making wheels of chilled steel instead of wrought iron. Another locomotive manufacturer, Septimus Norris, added a third pair of drivers in building the Chesapeake 4-6-0 which went into service on the Reading in 1847.
Until the mid-1850's, when locomotives began using coal, wood was the fuel that kept the engines running. Locomotive tenders were small and stops had to be made frequently at woodpiles and fuel stations. When the train paused to 'wood up', the conductor, brakeman, engineer and firemanand sometimes several of the passengers formed a line and passed the logs from one to another up into the tender. The roads used a great variety of logs, preferably oak and hickory, which measured from 18 to 48 inches long and from a couple of inches to a foot in diameter. A single locomotive consumed some 1500 cords of wood a year an amount of some consequence in those days of roads that ran just a few miles when it is considered that a cord is a solid pile of wood eight feet long, four feet wide and four feet high.
Wood gave way gradually to coal as fuel, and the 60's saw the substitution of steel for iron in railroading. Steel fire boxes, steel tires shrunk onto iron wheels, and steel tracks all accelerated the development of the steam locomotive. The Mogul 2-6-0, built to haul freight for the New Jersey Railroad and Transportation Company in 1867, won immediate popularity because of the greater weight it carried on its drivers, and the Consolidation 2-8-0 with its fourth pair of drivers was the standard locomotive for hauling freight for more than 25 years.
A whole new series of locomotives with wider fire boxes, bigger boilers, greater steam capacity, and wheels behind the drivers were developed in the last decade of the old century. These were the Atlantic 4-4-2, the Pacific 4-6-2, the Prairie 2-6-2, and the Mikado 2-8-2. Before the new century began, a 4-4-2 locomotive built by Samuel Vauclain pulled a six-car train 55 miles on the Atlantic City Railroad at an average of 70 miles an hour, at times reaching the remarkable speed of 115 miles an hour.
The new century ushered in more locomotive improvements. A pair of drivers added to the freight-hauling Mikado produced the 2-10-2 or Santa Fe type, used on that road, and the Pacific passenger engine became the 4-8-2 Mountain type. The Mallet 0-6-6-0 got steam for its two engines from one long boiler; the front engine was hinged to enable the locomotive to negotiate curves easily. The Mallets grew into 2-6-6-2's, 2-8-8-2's, and, on the Virginian Railway, into 2-10-10-2's with 20 driving wheels.
New methods were developed to produce more and better steam in the boiler, and further progress came with the invention of the automatic stoker, which spread a thin and uniform fire over the grates of the big new engines. The Lima Locomotive Company built a locomotive in 1925 with a four-wheel trailing truck carrying a bigger fire box with greater heating surface, steam capacity and horsepower, and a new series of locomotives roared into railroading. Classifications of these engines ended in 4: the 2-8-4 Berkshire, originally built for the Boston and Albany; the New York Central's 4-6-4 Hudson; the 2-10-4 Texas, used on the Texas and Pacific; the 0-8-4 Union; and many 4-8-4's combining the power of freight service with the speed of passenger service.
Mallets of the 2-6-6-4 and 2-8-8-4 types pulled strings of cars a mile long at 70 miles an hour. The Pennsylvania 6-4-4-6's, with 6500 horsepower, could pull a 1000-ton load at 100 miles per hour.
New methods of steel-casting made it possible to cast the engine bed or framework, previously composed of several hundred separate parts, in a single piece. Streamlining also made the steam locomotive more efficient by greatly reducing wind resistance and thus saving horsepower.
But improvements that made steam locomotives bigger and more efficient were not enough to sidetrack the approaching diesel-electric locomotive. The diesel engine was invented by Dr. Rudolf Diesel, who built a single-cylinder, 25-horse-power unit in 1897. Dr. Diesel disappeared mysteriously while crossing the English Channel in 1913, 12 years before the Central Railroad of New Jersey put the first diesel-electric, a switching engine, in regular service in this country.
The first passenger trains to use diesel-electric power successfully in main line service in the U.S. went into operation on the Burlington and Union Pacific railroads in 1934. Diesel freight locomotives were first placed in regular service on the Santa Fe in 1940, and during the 40's, a lamentable decade for steam railroad buffs, the steam locomotive began its decline.
Within 10 years after World War II had ended, many railroads were operating with diesel locomotives exclusively and more than three-quarters of all railroad service in the U.S. was being performed with mobile electric power produced by diesel engines.