Here's an picture of a old derrick with a small pumping unit that was powered by a rod line.
The rods and pump are not in this well. The rod that powered the pumping unit would have been hooked to the bottom end of the triangle that is part of the walking beam. The power house that powered this well would have been off to the left of this picture. The old center powers were a building that had a "one or two lunger" engine (oil field talk for a one or two cylinder engine). A one foot wide belt would run from the engine to a "Bull wheel" that would be 10 to 15 foot across. The bull wheel was horizontal. On the bottom of the bull wheel would be a small wheel about 4 foot across that had a offset crank to the main shaft that would move the rod to the well back and forth. When the power house bull wheel pulled on the rod the pumping unit would pull up on the rods in the well which pulled on the subsurface pump which pumped oil and water up the tubing to the surface and on to the stock tanks. When the power house bull wheel pushed the rod the pumping unit walking beam would lower the rods back into the well. The rod between the power house and the pumping unit was up off the ground. A 2 inch pipe stuck in the ground with a block of oak on top would keep the rod up off the ground.
Most of wells that were operated with a center power are all gone. The last one's I saw was southeast of Pampa, Texas back in the 1980's Most pumping units today are ran by a gas engine or electric motor. A electric motor is the best due to you can run the pumping unit a few times a day if the well only makes a few barrels a day and not wear out the pump, rods and tubing in the well.
I was a "company man" for Amoco and then BP and repaired many a well in my 30 years.
In the upper left is my pumping unit and a gas well "christmas tree" (painted red) and a production unit to remove the oil and water from the high pressure gas from the gas well. In the center is my "Tank Farm" with tanks for Propane, Diesel, unleaded gasoline and motor oil. The water and oil stock tanks for the oil and gas wells is behind the round ball propane tank and are painted gray.
Second picture shows the oil and gas well stock tanks and the production unit. The two smaller tanks are made by Lionel and the large tank is a 10" plastic pipe cap. The round propane tank was built from Alan Arnold's plans from the O gauge magazine.