"Pioneer Trail spans a distance of 25 miles, starting just east of Nevada City, and climbing along the current route of State Highway 20 to Bear Valley. There it departs from the highway and enters the South Yuba River canyon, where it climbs to join the Spaulding Lake Trail and the 41-mile system of non-motorized trails in the Grouse Lakes area."
East to west elevation gain: ~1850 Elevation loss: ~3300
Please note that at the time of this submission (5/31/20) Pioneer Tr can be found on AllTrails, however, their map is not entirely accurate and therefore is not recommended to follow. Specifically, the portion in Bear Valley is significantly off. The attached .gpx is recommended for better detail.
It is also noteworthy that this trail crosses several dirt roads and numerous dirt bike trails. While most junctions are marked, not all are. Downloading the .gpx to your phone is recommended.
Route submitted by Ben Mitchell