Last year marked the bicentennial of the world's first railway. In 1804, Richard Trevithick's "Penydarren" locomotive became the first in the world to run on rails when it hauled a train in Wales.

Less than 100 years later, thousands of fire-breathing behemoths were chugging across the United States daily. Approximately 640,000 steam locomotives were built worldwide between the mid-1850s and the mid-1950s. Most were assembled in the United States, England and Germany.

Three manufacturers dominated the industry in the United States: American Locomotive Co. (Alco, Schenectady, NY), Baldwin Locomotive Works (Philadelphia) and Lima Locomotive Works Inc. (Lima, OH). At their peak, each company mass-produced more than 1,000 locomotives annually. And, they were considered pillars of American industry. In fact, both Alco and Baldwin were part of the Dow Jones Industrial Average from 1916 to 1925.

Alco was the largest steam engine manufacturer in the world. The company was created after the merger of eight smaller locomotive builders in 1901. In the 1930s, Alco built numerous streamlined steam locomotives that pulled famous passenger trains, such as the Hiawatha and the 20th Century Limited.

Baldwin was Alco's main rival. The company was founded by a jeweler in 1831. Over a 70-year period, Baldwin built more than one-third of all locomotives in the Unites States. In addition, it exported hundreds of steam engines overseas.

Lima was the smallest of the Big 3 locomotive manufacturers. The company originated as a machine shop and started building steam engines in 1880. By the mid-1920s, Lima claimed 20 percent of the U.S. market. It was famous for producing special-purpose locomotives, such as rugged Shay engines used for logging and mining applications.

In addition to Alco, Baldwin and Lima, some large railroads owned and operated in-house facilities for building steam engines. However, the locomotive industry was extremely cyclical. For instance, in 1923, Alco assembled 1,392 locomotives. In 1924, it built 810 and in 1925 it built only 437. In 1933, the company produced just one locomotive.

"Since they mostly created customer products to special order, builders could not smooth out variations in sales by producing for inventory, nor could they rely on brand names or advertising campaigns to stoke demand," says John Brown, author of The Baldwin Locomotive Works, 1831-1915 (Johns Hopkins University Press). "Direct competition between builders waxed as sales fell and waned as they rose."

To supplement those sharp fluctuations in demand, the companies sometimes manufactured other products. For example, Alco produced a line of cars and trucks from 1906 to 1913. Lima built a popular line of steam shovels and construction cranes for many years.

Steam locomotive builders operated vast manufacturing complexes that comprised numerous buildings. For instance, Baldwin's shops were scattered across several city blocks. In the early 1920s, it opened a new 600-acre facility that included 100 acres of floor space and was dubbed "the best-equipped steam locomotive plant in the world."

Most facilities included a pattern shop, a foundry, a machine shop, a carpenter shop, a boiler shop, a wheel and flange shop, a bolt shop, a blacksmith and hammer shop, a tank (tender) shop, a truck shop, an erecting shop and a paint shop. Final assembly took place in the erecting shop.

Locomotive building was a labor-intensive process. While numerous machine tools were used to fabricate components, most assembly was done by hand. The typical steam locomotive weighed more than 100 tons and was held together with thousands of bolts and rivets. It took approximately 8 weeks to assemble a locomotive.

"Although basically a simple machine, the construction of a steam locomotive required a lot of careful organization," notes Philip Atkins, author of The Golden Age of Steam Locomotive Building (Atlantic Transport Publishers). For instance, Atkins says a standard 2-6-4 passenger engine built in 1934 required 27,000 distinct components, including 12,000 rivets, 3,500 bolts and setscrews, 3,350 nuts and 1,475 split pins.

"Locomotives were massive, complex and costly to make, requiring a large capital investment and an extensive labor force with intensive skills," adds Brown. "Engines were made to order, generally to custom or semicustom designs, and were quite literally ‘built'-assembled individually, piece by piece."

In 1850, Baldwin required 60 days to build a 22-ton locomotive. By 1900, its engines weighed an average of 65 tons, but still required 60 days to assemble, because many parts needed to be hand-filed and fitted together during assembly.

Despite being a labor-intensive industry, steam locomotive manufacturers developed a wide variety of production equipment to boost throughput. For instance, between 1850 and 1900, Baldwin improved its labor productivity by an average of 3.1 percent annually vs. 1.9 percent for the entire U.S. industrial sector. During the 1880s, Baldwin engineers received U.S. patents for tools such as a gang-drilling machine, which bored 20 accurately spaced holes simultaneously in boilerplate; large-capacity boilerplate shears; an automatic feed table for punching machines; and an automated mechanism for turning tapered bolts.

"The new machinery boosted speed and accuracy, particularly in boilermaking, which was notably labor-intensive," says Brown. "Although the new tools primarily enhanced productivity, some also took on a measure of the skill that heretofore had rested in workers' hands. For the first time in locomotive building, machines were displacing skilled men."

Steam locomotive builders were early proponents of flexible manufacturing. "In meeting customers' varied design needs, productive flexibility was essential," explains Brown. "To that end, the builders mostly used general-purpose machine tools, such as lathes, planers and slotters, adaptable to a variety of work."

Baldwin was one of the first manufacturers in the world to convert its factories from steam engine power to electric drive. In 1890, it built a new erecting shop that was large enough to assemble 75 locomotives simultaneously. It featured two huge electrically driven overhead cranes that reduced material handling and improved workflow. "Without electrification, the company simply would have sunk beneath the long-term increase in demand and the growing size and weight of [locomotives] during this period," says Brown.

Because of its conversion from gas lighting to incandescent lighting and arc lighting, Baldwin was able to switch from double shifts to round-the-clock operations. As a result of all those improvements, production climbed steadily from 517 locomotives in 1880 to 946 in 1890 to 1,217 in 1900. By 1906, new locomotives rolled out of Baldwin's erecting shop at the rate of one every 3 hours, 24 hours a day.

While customers around the world ordered uniquely different locomotives, Brown says the standardized methods used in production reduced "the constant variety and potential chaos to routine and order." Because of that consistency in the second half of the 19th century, Baldwin's product line grew from 12 to 118 classes built annually, while its finished locomotives weighed anywhere from 4 to 175 tons. At the same time, locomotive power output rose from 30 hp to 1,500 hp.

New assembly tools, such as steam riveters, promoted accuracy and standards. Machine-riveting produced uniformly tight joints, which improved boiler safety. Locomotive builders used large "bull" riveters to assemble boilers faster.

"Each consisted of a large cast-steel U-shaped frame that had one side firmly affixed to the shop wall and its base embedded in the shop floor, leaving the other half of the U as a free-standing post," says Eric Hirsimaki, author of Lima (Hundman Publishing Inc.). "Boiler shells were suspended around this post during riveting."

According to Hirsimaki, the largest of the bull riveters used by Lima had a 16-inch gap between the riveting machine and the bucking post located 19 feet above the shop floor. Rivets were placed in a small furnace next to the riveter and were heated to approximately 1,600 F. After an operator inserted a rivet into a hole using tongs, pressure was applied by the machine. The overlapping seams were riveted with two or three rows of tightly placed rivets. "Each of the bulls could generate 1,485 psi, although the exact pressure and time of application varied with rivet size," explains Hirsimaki.

The heart and soul of every steam locomotive was its boiler. This key structure was joined together from several smaller curved components, similar to the way an airplane fuselage is assembled today. The assembly of the boiler started with riveting individual longitudinal seams together with weld plates. Anywhere from six to 12 rows of rivets were applied to ensure a tight seal. A huge firebox was attached to the rear end of the boiler.

"After all riveting was completed, the inside corners of the weld plates were mechanically caulked by hand with an air hammer and caulking chisel," says Scott Trostel, author of Building a Lima Locomotive (Cam-Tech Publishing). "This provided the final seal. In later years some experimentation was carried out using a welded caulk bead, but due to metallurgical complications, Lima failed to advance this technology."

According to Trostel, "the noise in the boiler shop was almost unbelievable. The clutter of components, plates, partially assembled boilers and steel made it very difficult to walk through the building; and worse, it was also the highest source of occupational injuries in the complex."

While the boiler was being assembled, other major components, such as frames, wheels, cabs and tenders were fabricated in other buildings. Drivers were machined on boring mills and wheels were turned on lathes. Connecting rods, axles and other components were forged by steam hammers. The pieces were transported to the erecting shop by horse-drawn cart or a mechanical tugger for final assembly.

The typical locomotive required 10 days in the erecting shop. "Most visitors to the erecting shop [found] it a confusing bedlam of parts and men, a chaos of designs in varying stages of completion," says Brown.

"Of the more unique skilled tradesmen in the complex were the mechanics who assembled the locomotives," adds Trostel. "These craftsmen had to be well-versed in the assembly process since not all locomotives were the same size, [had the same] wheel arrangement or used the same items for their operation."

Labor rates were paid on a piecework incentive. "The assembly gangs came from a labor pool that did a special job on each locomotive," says Trostel. "These pools consisted of frame gangs whose job was frame assembly, driver gangs who placed the drivers and rods on the locomotive, pipe gangs for plumbing, lagging gangs for boiler insulation and jacket gangs for the outer sheet metal wrapper installation."

The first stage in locomotive erecting involved precisely aligning a pair of heavy frames on screw-type jacks and bolting cylinders to each side. Next, an overhead crane would position the boiler over the frame and lower it, where assemblers would bolt them together. Then, hundreds of flues would be attached to the inside of the boiler shell. Finally, the boiler and frame would be hoisted and placed onto a set of driving wheels.

Specialist gangs would then attach and test numerous boiler fittings. The boiler would be tested with hot water at 200 psi and any leaky flues or fittings would be caulked. Meanwhile, the most skilled assemblers in the plant attached connecting rods and valves, which had to be precisely aligned.

Various steam pressure and lubrication pipe lines were run along the boiler wall that would be hidden under the boiler jacket. Once plumbed, boiler lagging was added. This process required the attachment of wires around the boiler. Blocks of lagging were attached to the boiler. The lagging was made from asbestos, because "it was an excellent insulator, inert and fireproof in an environment where it would have to contain the heat of a fired boiler of between 400 and 500 degrees, and keep the exterior surface of the lagging at no higher than 100 degrees," says Trostel. "When the lagging was fairly well advanced, a boiler jacket would be applied. This was a sheet metal outer wrapper that covered the lagging."

Next, the locomotive cab would be attached to the rear of the firebox. Various throttles, levers, gauges and fittings in the cab were attached, including the main steam gauge, cylinder gauges, air pressure gauges and water level gauges. Assemblers would also add numerous exterior parts and fittings, such as lights, bells, whistles, brake rigging, valve gear, handrails, grab irons, running boards, fire grates and ash pans.

As a locomotive neared completion, heavy lifting slings would be positioned around it and attached to an overhead crane. The locomotive would be positioned onto a "ready track" and mated to its tender, which carried water and coal or oil. Draw bars were attached while water hoses and brake lines were connected. The locomotive was run out the door under steam power for the first time and run back and forth on a test track while it was checked for performance. After it passed inspection, a locomotive was send to the paint shop. Spray guns were used to paint large areas, such as the boiler jacket. Brushes were used to paint smaller parts and locomotive trim, such as white-striped drivers. The painting process included hand-lettering.

During the 1930s, American railroads slowly began to adopt diesel-powered locomotives, due to improved operating efficiency. However, it often required several diesels to replace the power of a single steam engine. And, it took several decades before steam fully replaced the nation's 50,000 steam locomotives.

The last steam locomotives built in the United States rolled off the assembly line in the late 1940s. Alco built its last steam engine in June 1948, while Lima's last locomotive left the factory in May 1949. Many of those locomotives stayed in service until the late 1950s.

Today, the unique sight and sound of steam locomotives live on in many museums and tourist railroads scattered throughout the country. Some steam engines pull special excursion trains along mainline routes. Only two companies currently mass-produce diesel locomotives in the United States: The Electro-Motive Division of General Motors (McCook, IL) and GE Transportation (Erie, NY). The industry is currently experimenting with hybrid diesels and alternative power plants, such as fuel cells and solar cells.