When steam locomotives were being used in the early days the steam locomotive had to stop every 7 to 10 miles for what was known is a water stop.
The steam locomotive would need to refill with water every 7 to 10 miles so that they didn't completely run out of water.
However later on the tender cars had water tanks on them so they could go much farther without needing to stop for a refill of water.
With the tender car and larger water tank the locomotive could go from 100 to 150 miles before they had to stop for water.
There were several water towers located along the railroad tracks to allow the steam locomotives to stop and fill up the steam locomotive with water.