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Some fun descents and one brutal climb in this loop through a once-thriving mining district.

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1,228' 374 m


448' 137 m


1,328' 405 m


1,373' 418 m



Avg Grade (4°)


Max Grade (14°)

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Old mining and ranch roads criss-cross this regional preserve offering mountain bikers miles of riding opportunities. This figure-eight loop gives an introduction to the area with some great views, fast descents and "The Wall" one particularly steep climb which is a series of three small walls with a couple breaks in between. The miners are long gone but the cows are still here... lots of cows.


The Stewartville Trail begins just south of the parking lot and spans the preserve in an east-west direction. It connected the former mining towns of Somersville and Stewartville. It gradually climbs through a small valley getting steeper as it reaches the top of the ridge at a gate. Just past the gate is the junction with the Ridge Trail. This loop section can be ridden in either direction but the clockwise direction is used here.

Nice views in all directions, with Rose Hill Cemetery in the distance looking west with Sand Creek Valley to the east and Mount Diablo to the south. Head left and UP the Ridge Trail. It's steep but short and the top is the high point of the ride.

Continue east as you mostly descend on a roller-coaster, ridge-top fire road. Views open up over the towns of Antioch and Brentwood out to the Sacramento Delta. One last twisty downhill brings you back to the Stewartville Trail.

A sharp right and you'll be heading south then west on this fast graveled section. Several trails branch off to old mining sites but are mostly dead-end trails. After passing a large corral, the Stewartville town site is reached. Nothing left but mine tailings. The road makes a sharp right at a boundary fence and begins the steep climb to the ridge. A couple switchbacks ease the grade but stopping to enjoy the view is advised. First to the top gets a choice spot on the rest bench.

It may be tempting to head straight down Stewartville Trail to the parking lot but the last loop offers more views and another fun descent. The Carbondale Trail starts with a short climb followed by a gradual descent to the River View Trail. Both trails offer great views over the Delta and the River View Trail is a fast and smooth descent, just watch for hikers and horses.

History & Background

The Black Diamond Mines Regional Preserve encompasses a coal mining area that once supported several towns. Sand was mined after the coal ran out to supply local glass factories. The visitor center near the start of this ride is worth a stop.


Shared By:

Bob Gardner

Trail Ratings

  3.3 from 6 votes


  3.3 from 6 votes
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45 Views Last Month
3,005 Since Feb 15, 2016
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Rest point at the top of the ridge. Good views of Mt. Diablo
Jan 9, 2021 near Clayton, CA
Near bottom of Stewartville Ridge Loop near trail to parking lot.
Jul 21, 2022 near Clayton, CA
Top of "The Wall". Ridge Trail.
Jan 15, 2022 near Clayton, CA
The Stewartville "Wall" as seen from the Ridge Trail.
Feb 23, 2016 near Clayton, CA
Heading up River View Trail.
Feb 23, 2016 near Clayton, CA
Carbondale Trail near Stewartville Trail junction
Feb 23, 2016 near Clayton, CA


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