The Chino branch was basically a large loop, in the shape of an inverted shed. It connected to the SP's Sunset route main line at both ends. The UP's Los Angeles & Salt Lake was built parallel to (and south of) the SP Sunset route in the area, so each end of SP's Chino branch crossed the UP.
The branch served industrial and agricultural customers in western San Bernardino County.
Most of the eastern portion of the branch was abandoned in 1940 per the ICC notice, but a short segment was still in service when the pictures were taken. The abandoned segment has been replaced by residences and businesses; no traces were located. The still-active western end has actually expanded, with several long industrial sidings added over the years.
Thanks to Mike Palmer for contributing information about this route.