Monroe Ridge / Marshall Monument Trail Loop Professional Review and Guide
"Climb through oak woodlands to viewpoints above the snaking American River, then tour a historic gold rush town, including the site where the precious metal was first discovered in 1848. You can still pan for gold along the South fork American River in Marshall Gold Discovery State Historic Park, but arguably that's not the most valuable thing that can be gleaned from these hills in modern times. The canyon walls hovering over historic Sutter's Mill offer spectacular views up and down the river valley.
The trail climbs the steep canyon wall via a number of switchbacks, winding through stands of red-barked mountain manzanita, oaks, and, in its upper reaches, ponderosa pines. Road noise from CA 49 filters up through the trees, but fades as you gain altitude and distance."