Railroads in the 1840s saw a new industry begin to flourish and blossom. Many advances in railroad technology were achieved during the decade, more companies would be born in the decade (including some quite famous) and, of course, more mileage was added to the network so much so that by the end of the decade trackage had more than tripled from the beginning of the decade. Following the creation of the Baltimore & Ohio, South Carolina Railroad and success of the steam locomotive railroad mania struck the nation as a fast an efficient means of moving goods. By 1840 the states east of the Mississippi River boasted over 2,800 miles of track and this number quickly rose as the decade wore on.
During these early years much of the trackage was still disconnected with most concentrated in the Northeast and the rest scattered in the Southeast and Midwest, much of which ranged in track gauge from the standard 4 feet 8 1/2 inches to six feet. Railroads of this era could best be described as still in the experimental stage as there was little government oversight and as a result the public suffered from unsafe practices and the unwillingness of railroads to interchange traffic with another due to the greed and selfishness of owners. Despite this problem there was still nothing faster to move people and goods than the new technology of railroading as by 1850 every state east of the Mississippi except Florida could boast at least a few miles of railroad.
Along with this flurry of new track construction surprisingly improvements in the infrastructure followed rather quickly. Unstable and dangerous strap-rail (which was simply thin pieces of iron attached to wooden planks) that caused the deadly phenomenon of "snake heads" (which was an iron strap that came loose and was peeled upward by a passing car wheel it acted as a can opener when the next train passed over the broken rail literally ripping the train apart and almost always killing passengers and sometimes crewmen) was replaced by solid iron rails. Not long after the introduction of solid iron rails the "T"-rail was introduced, developed by Robert Stevens president of the Camden & Amboy Railroad, it was a revolutionary design still used to this day.
Other infrastructure improvements during the 1840s included crushed stone, called ballast, as a support base for rails and crossties (the ballast also facilitated in proper drainage of water away from the rails), which supported the rails giving them more rigidity and strength. During the decade freight and passenger cars became end-to-end platforms with double-axled trucks (the wheel assembly which housed the axles) located on each end. Also, the now classic 4-4-0 "American Type" steam locomotive was developed, by Henry R. Campbell, at the end of the 1830s in 1839 and became the most commonly used and best recognized locomotive of the 19th century.
Its front "bogey" truck assembly swiveled allowing the locomotive to easily negotiate curves (the concept would be applied to almost all future steam locomotives used in main line service), which led to more powerful and efficient designs like the 2-8-0, 2-8-2, 4-6-0, and many others. Railroads of the decade also saw hundreds of new companies chartered including the predecessor to the Pennsylvania Railroad in 1846. Also, the seeds were in place for what would become the New York Central in the 1850s, the PRR's primary competitor in the east. The other major eastern trunk line, the Baltimore & Ohio, continued to push westward during the decade reaching Cumberland and beyond by 1850.
What transpired in the 1840s led to an even greater explosion of new railroads and construction in the 1850s. Aside from the tripling of new mileage at the beginning of the decade and another tripling by 1860, this time period of the 19th century saw further technological improvements so much so that train speeds had increased to the point that one could reach Chicago from New York in just two days or so. The 1850s would also see railroads break across the Mississippi River into Texas and plans made for the push across the continent to California and the west coast (as gold was discovered there during this time).