While not a particularly good trail by itself, Extension Mill provides a quick, direct link from the eastern end of the Upper Flume Trail
to Prospect Hill Road
which in turn connects to Side Door
and other French Gulch trails.
Extension Mill Road (GH 25) begins on the east side of Gold Run Road
0.2 miles west of the Upper Flume Trail
junction. The wreckage of the mill is still visible on the southeastern corner of the intersection. There is a post and carsonite marker at the northern end of the trail.
Extension Mill climbs steeply first crossing Preston Way
(GH 23) after a few hundred feet, then merges with Fall Classic Trail
on the west after 1/3 mile. Extension Mill then climbs past Draw Road
(GH 24) and two additional non-system doubletrack roads on the left (east side) of the trail, crossing below a power line before leveling off. 1/4 mile after leveling off, Extension Mill terminates at Prospect Hill Road