Locomotives first came into use in the United States in the early nineteenth century, inspired by the steam-powered locomotives that had appeared on England's first common-carrier railroads and roads for coal mines. In 1825 Col. John Stevens of Hoboken, New Jersey, built an experimental locomotive and demonstrated it on a circular track. The Baltimore and Ohio Railroad, chartered in 1827 as the first common-carrier railroad in the United States, faced the question early on of what form of power to use. Peter Cooper of New York City, a director of the railroad, built the Tom Thumb for demonstration purposes. Success was sufficient to lead the railroad to sponsor a competition to secure a commercially useful locomotive. Phineas Davis, of York, Pennsylvania, won the competition in 1831. His York was the predecessor of a considerable group of vertical-boiler locomotives called "grasshoppers" that had walking-beam power transmission. Meanwhile, the West Point Foundry in New York built Best Friend of Charleston, the first locomotive intended for commercial service, for the South Carolina Canal and Railroad Company.
Some companies imported locomotives from England during the early experimental period, notably for service on the Camden and Amboy Railroad and for tests on the gravity railroad of the Delaware and Hudson Canal Company. These imports proved ill adapted to the light and uneven track of early American railroads and to the sharp curvature and heavy grades that often were encountered. To adapt to these conditions, American locomotive design began to depart from British practice. American designers used a leading truck to improve track-keeping qualities, applied headlights and cowcatchers, and developed various devices such as the Baldwin "flexible beam" truck to lend curve-keeping ability to freight locomotives of six and eight-coupled design.
The early locomotive builders—Matthias W. Baldwin and William Norris of Philadelphia, as well as Davis—began as jewelers and shifted to machine-shop practice. Baldwin and Norris proved to be highly inventive contributors to locomotive development. The Baldwin works, first in Philadelphia and later in Eddystone, Pennsylvania, became the nation's largest locomotive builder. Norris developed some early export business: one of his locomotives proved to have the ability to haul a train up the inclined plane of the Great Western of Great Britain; others supplied power for the first railroad built in Russia.
Numerous small locomotive works operated in the early period, ranging from the William Mason Company at Taunton, Massachusetts, to the Richmond Locomotive Works at Richmond, Virginia. Some of these ultimately disappeared; a number were merged to form the American Locomotive Company, headquartered at Schenectady, New York, second of the country's great locomotive builders. Several railroads built locomotives in their own shops but none so many as the Pennsylvania Railroad, principally at Altoona, Pennsylvania. The Pennsylvania also pioneered the standardization of locomotives beginning in the 1870s and contributed much to the improvement of locomotive design.
The steam locomotive demonstrated its speed capabilities early, having attained sixty miles an hour by 1848. Hauling capability developed more slowly. The typical locomotive for freight and passenger work in the 1870s had four driving wheels (4-4-0, or American type) and a tractive effort of 8,000 to 12,000 pounds. Locomotives for heavy freight work were built with six or eight driving wheels. The Consolidation type (2-8-0), first built for the Lehigh Valley Railroad in 1866, became the most popular. Tractive efforts of leading specimens of this locomotive type increased from 24,000 pounds in the 1870s to 46,000 pounds by the end of the century. Apart from gradual perfection of design, improvement of materials, and increase of boiler pressures and weight on driving wheels, the greatest early post–Civil War challenge was the development of suitable grates and fireboxes for burning coal in place of wood.
Unlike stationary or marine plants, locomotive power plants needed to fit into a small space and have a weight that tracks and bridges could carry. They also had to function while exposed to the weather and the vibration encountered in moving over the road. By the end of the century, at a time when railroad traffic was burgeoning, the locomotive had attained close to its maximum capacity under conventional design practice. Between 1895 and 1910, a series of innovations—trailing wheels that allowed a wide firebox to be carried behind the rear drivers and the boiler to be lengthened, the brick arch, piston valves, and outside valve motion—enabled engineers to more than double the locomotive's tractive power.
Most important was the introduction of superheating, which delivered very hot, dry steam to the cylinders, reducing condensation and increasing cylinder horsepower within existing dimensions. In 1904, the first Mallet type of articulated locomotive came into service on the Baltimore and Ohio Railroad. This method utilized two systems—one of compounding (use of steam first in high-pressure cylinders, then a second time in low-pressure cylinders), developed in Europe; and one of attachment, in which the front engine and driving wheel were set by a pin to the main frame so it could swing with curvature. Of particular use on lines of heavy gradient, the articulated locomotive increased rapidly in size, and, by 1920, some models exerted 120,000 pounds of tractive effort when working single expansion. The mechanical stoker, essential for firing such locomotives, had been perfected by then. Improved lateral-motion devices made the ten-coupled nonarticulated locomotive more practical, and typical examples of the 2-10-2 on eastern roads developed up to 84,000 pounds of tractive effort prior to World War I.
The need for greater horsepower to permit sustained high-speed operation with heavy loads led to a series of experiments from which emerged the first "superpower" locomotive, completed by the Lima Locomotive Works in 1925. This locomotive combined the elements already noted with a feedwater heater and four-wheel trailing truck to permit a much larger firebox. It became the prototype for hundreds of locomotives of the 2-8-4, 2-10-4, and, ultimately, 4-8-4 types that allowed for a major acceleration of freight service with greatly improved efficiency.
By this time, the manufacture of locomotives for main-line railroad service was confined to three outside builders: Baldwin, American Locomotive, and Lima. Railroad shops, especially those of the Pennsylvania, Norfolk and Western, and Burlington Railroads, continued to build new power. Railroads that built power also procured locomotives from outside builders. Railroad motive-power departments and the outside builders shared in the engineering, from which improved design emerged. But the manufacture of specialty items—such as superheaters, feedwater heaters, stokers, and boosters—moved more and more into the hands of the supply industries.
The Great Depression of the 1930s brought a near-paralysis of locomotive building during the years 1932– 1935. The revival of railroad purchasing, although slow, was marked by the development of a new generation of locomotives—single-expansion articulated models specially made for service on the western transcontinental roads and several of the coal-hauling roads in the East. These locomotives combined the starting tractive effort of the Mallets with the speed capabilities of the later superpower locomotives. In these designs, the steam locomotive reached its peak of development in the United States. Locomotives of this genus, differentiated somewhat in design to meet intended service conditions, could haul 18,000 tons or more in coal or ore service, or move a 7,000-ton manifest freight at seventy miles per hour.
World War II interrupted steam locomotive development. So great had been the progress in diesel locomotive development that many railroads never bought steam-powered locomotives again. There were exceptions, especially the coal-hauling railroads of the Northeast, and several advanced designs were engineered for them. Locomotives built to those specifications, however, had a short life, as the superior efficiency of the diesel locomotive in all service classes was recognized. The last steam locomotives built by Baldwin for service in the United States were delivered in 1949, and Lima's last locomotive for an American railroad was the same year.
The steam locomotive was rugged, long-lived, and capable of being designed for any type of service. Hundreds of steam locomotives operated for forty years and more, often with few modifications. But the steam locomotive was never a particularly efficient machine, delivering, at the peak of its technical development, power at the drawbar equivalent only to 12 to 13 percent of the energy latent in the fuel. Since the greatest energy losses were in the cylinders of the reciprocating machine, late experiments were undertaken on three of the coal-hauling roads with steam turbine locomotives. This effort was made obsolete by the proven success of the diesel.
Straight electric locomotives were never extensively employed on American railroads. Although the Baltimore and Ohio used them after 1895 in its Baltimore tunnels, the Pennsylvania electrified the approaches to Pennsylvania Station in New York City in 1908, and the suburban lines out of Grand Central Station were electrified in the period 1906–1913, use of electric locomotives was always confined to special circumstances. The Milwaukee employed them over 641 route miles across the Rocky, Bitter Root, and Cascade mountain ranges; the Great Northern between Skykomish and Wenatchee, Washington; and the Norfolk and Western and the Virginian on heavy-grade lines. The outstanding electrification was that of the Pennsylvania between New York and Washington, which was later extended over the main line to Harrisburg. The first segment, between New York and Philadelphia, was opened in 1932. Exceptionally heavy traffic density was considered to justify the investment in power transmission and distribution. Of the several types of locomotives employed on this 11,000-volt alternating current electrification, the GG-1 was outstanding, developing 8,500 horsepower on short-period rating and working both freight and passenger trains. Most of these locomotives were still in service forty years after the prototype was delivered.
Changes in technology resulted in renewed consideration of the advantages of electric propulsion. The mercury arc and, later, the ignitron rectifier, superseded the motor-generator set in locomotives powered by alternating current. The use of commercial frequencies became possible, and several western roads instituted studies of electrification of their more heavily trafficked main lines.
In the 1970s, except over the limited electrified mileage and on a few short lines, all American railroad service was powered by diesel-electric locomotives. These used diesel engines to power generators that supplied direct current to the traction motors. The first such locomotives were delivered for switching service in 1925 and Baldwin and American Locomotive both began manufacturing them. However, the electric motive division of General Motors pioneered the application of the diesel to both passenger and freight road service in the late 1930s. In the 1970s, the business was dominated by General Motors and General Electric, the latter a past supplier of components to other manufacturers.
The diesel locomotive has the advantage of high efficiency and availability compared with the steam locomotive. It can operate in multiple units, with any number of locomotives being controlled by a single engineer. Mid-train helper locomotives are controlled from the head locomotive, making for a better distribution of power in long and heavy trains. The problem of water supply—a serious issue for steam locomotives in many parts of the country—was eliminated. Unlike steam locomotives, diesels have been standardized by manufacturers, and traction motors and other components can be removed and replaced by standby units to keep the locomotives in service. Although the first diesel road-freight unit was tested in 1940, third-generation diesels were coming into service in the 1970s. Single units could generate more horsepower than four units of the original 5,400-horsepower freight diesel; however, locomotives in the 2,500-horsepower range remained popular because of their versatility in the systemwide locomotive pools that most railroads employed in the mid-1970s.
Always in need of advanced data processing techniques, railroads were a leader in adopting computerized "total information" systems. Such systems use computers at each terminal or freight-yard office to report the action of every car to headquarters, which then generates reports on a variety of aspects of locomotive activities. By the end of the 1980s, most major North American railroads were developing systems that would allow their freight customers to transact business electronically, and passengers can reserve seats and berths electronically as well. Computerization allows railroads to track the mileage and maintenance requirements of each locomotive so overhauls can be based on need rather than at arbitrarily chosen intervals (as was the case). Overall, computers have facilitated significant advances in railroad operations, cost efficiency, and service.
Bibliography
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