The Industrial Revolution of the 19th century was a tremendous leap forward and there was no greater factor that progressed this revolution than the steam engine.
The power of steam should not be underestimated. When a closed container that contains water boils to the point that it converts to steam, it’s volume increases and if the container was initially fully filled with water, then the expanding vapor will not have enough room to expand; hence, it will push itself against the container’s walls until the its structural integrity is compromised, resulting in the container exploding.
And that is exactly what the engineers did when creating the steam engine. Credit is given to George Stephenson and Robert Trevithick in the 1800s for their work in pioneering the functionality of the steam engine. They harnessed the power of steam by boiling water (hence the name boiler in a locomotive engine) and opened a vent in the container for the hot steam to exit. They piped this exiting steam to mechanisms that would turn the wheels. The faster they could boil the water to produce steam, the faster, actually harder ( equivalent to voltage in an electrical wire), the steam would push out and the more power is applied to the wheels.
This led to the invention of the steam locomotive, steamboat and industrial machinery that advanced the manufacture of a large variety of products. But is was the locomotive that was responsible for cities to grow and people to go cross county much faster than they did on a horse. (Steam engines used to be called the iron horse.)
Scottish Inventor James Watt (January 30, 1736 – August 25, 1819) came up with a relationship between the steam locomotive and the power of a typical horse; specifically, 1 HP (horsepower) is equivalent to a horse moving 75 kilograms (165.32 lbs) a distance of 1 meter (3.28 feet) within 1 second. An example would be pushing 165 lb piece of concrete 1 meter in 1 second. And a typical steam locomotive is equivalent to about 1000 horsepower, so that equates to 7,500 Kgs moving 1 meter/second or 75 Kgs moving 1000 meters/sec. Example: Pushing 16, 534.68 lbs 1 meter/sec. In 60 seconds, you would have pushed the 16,000 lb concrete 60 meters (197 feet). That means that every minute, 16,000 lbs is moved about 200 feet.
But steam locomotives are complex. They can contain many wheels. The more wheels, the more power the engine has. For example, A 4-8-8-4 locomotive contains non powered four wheels, which help support the engine in the front and is called leading truck, two sets of eight driving wheels under the boiler, which are powered by pistons that move from the steam that is fed to it, and a non powered four-wheel trailing truck, which supports the crew cab and rear firebox area. So for a 4-8-8-4 engine, there needs supporting wheels in the front and back with the steam power going to the eight wheels in between them. This particular type of locomotive is called Big Boy and was the most powerful set of steam locomotives ever built.
Less powerful were the 4-6-2 steam engines and many were made around the world.