Thomas Reserve Trail to Williams River Overlook and back.  Two major climbs:

The big one:
Elevation 3610 ft to 4270 ft = 660 ft in 2.5 miles (5.0% grade)

The moderate one:
Elevation 4230 ft to 4520 ft = 290 ft in 1.6 miles (3.4% grade)

(plus a few smaller/shorter grades)