As I see history, the modern plow and the mechanical loom were transformative. The telegraph was revolutionary. Mechanization transformed large economic sectors so that in a few generations the farming and textile industries became almost unrecognizable. Even while their products, cloth, meat, flour, remained much the same the workforce, the economic geography, the relative costs of production (and thus the product mix), the economic demand for output of other industries, the range of products which could be supplied to other industries in addition to end consumers all changed dramatically.
The telegraph was something else. At first glance it does not seem to create anything new; what is telegraphing but a faster and more expensive alternative to the stage coach and the packet ship? It is true that the commodity being transported is the same information as had been carried from town to town or across the Atlantic and which kept business and government functioning in past generations.
Unexpectedly, telegraphy was creating a new and intangible product in the combination of information and time. This new product transformed how every other business behaved. In a sense the telegraph changed "everything" because it touched everything endeavor either directly (as in the case of large-scale manufacturing or warfare) or indirectly (as for the local blacksmith who had improved access to materials). What is more, the existence and utilization of the telegraph changed the public sense of time and possibility thus altering the underlying civilization.
Using this distinction one might argue that the telephone was transformative. Taken as a whole it has consisted of a long series of improvements, even transformations, to the telegraph.
Now what about the railroad? The underlying idea of carriages on rails rather than mud was important and transformative. (It was also centuries old by the 1800s and repeatedly improved.) But the railroad as it was implemented was not simply carriages on rails. It was also mechanical locomotives instead of horses and oxen, which was revolutionary, it was the revolutionary advances in iron and steel production, and it was the telegraph. Railroads would likely have existed with rails and horses but only as an incremental improvement over previous transportation methods. Railroads would likely have spread without telegraphs but they would never have realized the speed and efficiency of tracking, sorting, and routing every shipment across continental distances.
From this point of view the railroad was not just one development, however transformative. The railroad was a revolutionary combination of revolutionary and transformative changes which together restructured the entirety of modern society all in a small number of decades, mostly 1830 to 1890.