In the steam-locomotive era on railroads (1830-1955), the fireman was not only the one who stoked the boiler and fed it water to make steam, he was also the co-pilot of the locomotive. The fireman - all at the same time - managed the combustion and steam production of a 1000- to 6000-hp power plant and helped the engineer running at high speed in identifying signals, watching at road crossings, and watching for hazards or obstructions on the right-of-way.
A large steam locomotive from the early 1920s-1950s was often equipped with a steam-operated "automatic stoker" to feed coal into the firebox, since a human fireman could not physically keep up with a boiler much over 2500 horsepower.
The automatic stoker - which combined an augur screw to convey the coal from the tender up to the firebox and a system of small steam jets to "spray" the coal more-or-less evenly onto the broad surface of the fire - was not "automatic" at all. The fireman had to manually and adroitly manipulate a bank of control valves, first, to move the coal through the augur at the correct rate of fuel flow for the energy being demanded from the boiler, and second, to properly spray the coal over the fire to keep the depth of the burning coal as even as possible over the full expanse of 70 to 125 square feet of surface area.
It took great skill, honed over many years. The great trick was accurately estimating, well ahead of time, the fuel rate needed for widely varying power demand from the locomotive.
Coal rate, and steam rate, was maximum at high power output, as when climbing a steep grade for example. But the locomotive and train topped the grade and power demand suddenly decreased. In fact, locomotive power demand constantly changed, from zero to maximum, and varying widely in between. The skilled fireman not only had to successfully adapt to each change in demand, he had to "pro-actively" anticipate the changes in advance so as not to stress the boiler with wild pressure swings.
Hence a fireman had to "know the road" just as well as the engineer, knowing every mile of the route - not only where the steep upgrades and downgrades were, but everywhere on the route where speed-limits would change and thus where power demand would change, mile by mile.
The fireman's "scoop" (never a "shovel") was still required. The fireman used it manually to build up the fire at his locomotive's originating terminal. Building-up a banked or ebbing fire to a heat sufficient for heavy duty could take 30 minutes or more of strenuous but sophisticated effort.
Critical for both locomotive performance and safety, the fireman also managed the water level in the boiler: too much water and the locomotive could not steam properly; too little and the boiler exploded - literally - and with colossal force.
The scoop was also needed several times each hour to "trim" the fire, putting coal onto thin spots in the 'firebed' (the burning bed of coals), and getting rid of uneven places on the firebed. A long 'firehook' was used to pull out 'clinkers' - pieces of fused silicate which often built-up over time in a hot coal fire.
Firebox temperature reached 2000 to 2300 degrees Fahrenheit, for a steam locomotive working hard.