This article serves to elucidate the eras we selected for North America. Here is what we came up with:
- (I) Early Steam (1835 - 1900). From the introduction of the steam engine in the 1830s, railroads and equipment took many shapes and forms. At the start, rail gauge was not standard, not was even the basic appearance of the locomotive. If it worked, it was used. During this period (by 1840), locomotives assume a 'normal' appearance. Towards the end of this period (around 1885) we see the standardization of gauge at 1435mm (4' 8 1/2"). This in turn allowed more and more mass production of equipment due to the fact that a given locomotive could run anywhere. The United States was now crisscrossed with competing routes which turned the railroads' attention to power.
- (II) Late Steam (1901 - 1938). The railroads were rebuilt to be straighter, flatter and consequently faster. Most locomotives were now painted in plain black paint (in main due to the Panic of 1893). Standardization now was applied to couplers, air brakes and rules for interchange. Heavyweight steel passenger cars became common and we now see the first steel rolling stock. Steam locomotives become large, powerful and efficient.
- (III) The Transition Era (1939 - 1957). The second world war changed everything. However, many of the major changes that occurred during the war were glimpsed in the late 1930s with the first diesel locomotives and early lightweight passenger cars. The war simply put into high gear the changes that were already occurring. It is during this period that diesel and steam motive power shared the rail network.
- (IV) Second Generation Diesel (1958 - 1978). Steam is mostly dead or dying, but the development of diesel power is very rapid. We see low-nosed hood units take over and unit trains become ubiquitous. TOFC appears and mergers run rampant. Passenger service collapses due to the interstate highway system and Amtrak steps in.
- (V) Modern Diesel (1979 - Today). Cabooses and roof walks are now gone. FREDs have arrived. Containers are everywhere and are frequently stacked. A focus on cleaner burning diesels changes the way engines are designed.