Parking is at the end of Green River Road beside the eastern end of the Santa Ana River Trail.
The first mile is along the Santa Ana River Trail, directly beside State Route 91.
A gazebo with an interpretive sign marks the point where you cross beneath State Route 91 and meet the real trail.
On the south side of the freeway is the entrance to this rural portion of Chino Hills State Park.
The path to the waterfall soon leaves pavement and joins a dirt track heading into the rugged hills.
Red stemmed filagree growing along the Big Mo Trail.
The trail parallels the wash for a while before ending altogether and leaving the wash as the only route.
Wildflowers grow in the wet and shady canyon.
Follow the wash upstream.
The Coal Canyon waterfall, a 20-foot falls running over a mineralized ledge.
If you are underwhelmed by the waterfall, just remember that it technically lies in the Inland Empire.