Yuma was first settled as the best natural crossing of the wild Colorado.  Protection of the settlement and the supply route into the SW territories made it a significant army outpost and supply depot.   The Quartermaster Depot is well worth a stop.  Our guide did a great job telling the story of this place as materials movement evolved from overland from the west coast, to steam ship around Baja to rail.  Pretty impressive.

Of course, the trains came through here too

Pivot point plaza preserves the one remaining relic of early rail travel across the river. A huge concrete pylon that provide the support for the early pivootong bridge that let steamships pass.