Original steam locomotives could only go a fairly short distance before needing to replenish their water supply. The solution was to add a "tender car" behind the locomotive that carried additional fuel and water (there was a water tank under the wood or coal you see piled in the car behind the locomotive in old western movies.)
Even so, that only stretched the range to maybe a hundred and fifty miles or so between top-ups. Out in the west, this might not be far enough to get you to the next station, so the railroads built fuel and water stops at regular intervals along their routes where the locomotive could top up its tender. You've seen those water towers with the long spout that the engineer could jerk out over the tender to dump water into its tank, right?
Little hamlets would often spring up around these fuel & water stops, even though they didn't have an actual train station...
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