Smithfield Canyon Dirt Road

From the first dirt parking lot before the campground, start hiking up the road until it crosses the creek to the left on a nice bridge, then curve around to the right as the road continues up past the creek. The road then continues pretty obviously following the creek through the canyon where you can see plenty of beautiful sections of the creek, some really cool rock formations right next to the road, and even an old abandoned mine shaft (it has been sealed up) about a mile and a half up or so from the parking lot. The trail continues from here, following the creek until you eventually cross the creek over a culvert and finish up in the parking lot that leads to the actual Smithfield Canyon Trail (where you could continue your hike, if desired).