Max Weber, considered to be the father of modern sociology alongside Émile Durkheim, wrote a classic of economic history, General Economic History (German: Wirtschaftsgeschichte).
Weber concludes chapter 25 (“Free Wholesale Trade”) with:
The railway is the most revolutionary instrumentality known to history, for economic life in general and not merely for commerce, but the railway was dependent on the age of iron; and it also like so many other things, was the plaything of princely and courtier interests.
Max Weber, General Economic History, Collier Books, Third Printing, 1966, page 221.
Zooming out you may intuit that these narrow gauge explanations are inadequate but much better than nothing. We are faced with the problem of connecting railroads and the Iron Age to larger transformations from which these railroads were born.
Your high school history book might mention Abraham Darby III; to quote Wikipedia:
He built the largest cast iron structure of his era: the first cast-iron bridge ever built, as a crossing over the Severn near Coalbrookdale. The bridge made it possible for the village of Ironbridge to grow up around it, with the area being subsequently named Ironbridge Gorge.
He was the third of four men of the same name, all English ironmasters, from several generations of a Quaker family that played a pivotal role in the Industrial Revolution. Without James Watt, there would be no steam engine; without which, there would be no railroad. Watt in turn improved upon the Newcomen atmospheric engine, while consulting other scientists.
Despite the brilliance of Watt’s engine, however, without the financial backing of Matthew Boulton, it might have been a failure.
If you read Watt and Boulton’s correspondence, Watt is always thinking locally, whereas Boulton is already talking about selling the invention globally. This is the ecosystem in which Weber’s economic observations reside.
Weber leads up to the point of the importance of railroads by discussing the evolution of land transport.
Land transport also remained as before. The post produced no change; it merely forwarded letters and small packages, but did not concern itself with large scale production, which was decisive for economic life.
Only the roads underwent an extraordinary improvement, through the construction of turnpikes. In this the French government under Sully took the lead, while England leased the roads to private enterprisers who collected tolls for their use. The building of the turnpikes wrought a revolution in commercial life comparable to no other before the appearance of the railways. There is no comparison between the present density of road traffic and that of this period. In 1793, 70,000 horses went through the little town of Lüneburg while as late as 1846 only 40,000 were used in freight transport in all Germany. The costs of land carriage amounted to ten or twenty times the freight on the railways at a later time, and were three to four times as high as the charges for inland shipping at the same period. A half billion ton-kilometers was the highest figure for transportation for the movement on land in Germany, while in 1913, 67 billions were carried on the railroads.
Max Weber, General Economic History, Collier Books, Third Printing, 1966, page 221.
Weber also connects railroads with the atmosphere of speculation:
Such speculation underwent an enormous expansion with the building of railroads; these provided the paper which first unchained the speculative urge. Under the head of goods, grains, and a few colonial products available in large volume, and then other goods, were drawn into the circle of exchange speculation during the 19th century.
Max Weber, General Economic History, Collier Books, Third Printing, 1966, page 219-220.
Everything is connected to everything else, and without realizing this truth and sensing the underlying transformations, you cannot get a clear signal from history.