This spur line was used to reach produce distribution warehouses, but it rarely sees service. It previously branched from Yuma's "East Yard" (the perimeter of which is clearly visible in satellite imagery); however, East Yard has since been abandoned, leaving only the Union Pacific mainline and a handful of sidings to nearby industries.
At one point, this spur extended further south another mile to the Marine Corps Air Station. That extension has been abandoned, however remnants of rails track are still in place for a couple blocks.
Thanks to Mike Palmer for contributing information about this route.