These two operations were followed by the Mohawk & Hudson Railroad of 1826, the first chartered system in the United States to actually be constructed, and the Baltimore & Ohio Railroad of 1827, which holds distinction as the country's first common-carrier. The M&H later became part of the massive New York Central System while the B&O maintained its independence for many years until finally disappearing into CSX Transportation during the 1980s. As demand grew so did the need for more specialized car types and improved construction techniques. Early railroad cars, as mentioned before, were simple things, usually with only one axle attached rigidly to each end of the car.
A need for improved designs also came about due to ever-increasing loads. As this occurred it became apparent that the single axle could not cope. Cars equipped with them would often bend around curves and since the axles were rigidly mounted to the car’s frame there was no cushion for the freight, which was often damaged by the time it arrived at its destination. The two-truck car (which used two sets of trucks, or wheel housings, that held two axles each with each car carrying eight total wheels) is what you commonly still see on today’s cars and were invented as early as the 1830s by the Baltimore & Ohio. This concept was a vast change from English designs and became one of the most noticeable differences between American and British railroad practices.
The two-axle truck quickly caught on and was found in widespread use by the end of the 1830s thanks to its ability to more evenly distribute weight, handle heavier loads, provide better stability for the car, and offer improved cushioning for freight with springs mounted in-between each side of the truck assembly. Following the two-truck concept, car technology began to improve and became increasingly larger for heavier loads as locomotive horsepower increased. In spite of this specialized cars to handle different types of freight remained relatively few for many years, partially hindered by the railroad industry’s conservative views on such and its interest in redundancy to keep costs down (while railroads have always been conservative and “archaic” in this manner they have also had their reasons being that railroading in its very nature has nearly the highest cost of capital of any industry and relies on economies of scale to remain profitable).
One of the first specialized cars developed out of the flatcar was the gondola of 1830 followed by the covered gondola soon afterwards. This was essentially the birth of the boxcar, which could now handle covered loads and keep sensitive freight from being damaged by harsh weather conditions or other unseen forces. The hopper car was also developed around the same time; its history dated back to the 1820s when small jimmies (a two-axle, open-air wooden car with sides that could be unloaded by gravity via doors at the bottom) were used to transport coal but the first true car came about in 1840 when a larger design could handle heavier loads while offering a more efficient means of unloading its product.
In any event, the next major milestone in car development was the switch from wood to iron/steel in construction, which began to appear in cars beginning during the 1880s. This first use of iron was found predominantly in areas of the car pertaining to structural integrity such as sills and trusses. Eventually, steel became the preferred means of all car construction due to its superior strength. Still, even though all-steel cars became favored by the early 20th century those made from wood remained in use as late as the 1960s until their age forced them into retirement (today the Federal Railroad Administration [FRA] has set a 50-year “shelf life” standard for cars before they must be retired, with roughly ten years between major overhauls while in service).
While cars continue to advance and better designs will continually come about making them of higher quality and able to haul heavier loads, as has been the case since railroads were born (and some railroads have even fabricated their very own cars such as the Baltimore & Ohio and Pennsylvania Railroads) the basic designs will likely continue to fall into one of six categories; gondolas, hoppers, tank cars, well and spine cars, boxcars, and the common flatcar. So, look for these types of freight cars rumbling along on railroad tracks near you throughout the foreseeable future!
Related Reading You May Enjoy