Entry No. 66 — the Los Angeles file — filed under: ruins
Coquina Mine
Located in the Marr Ranch Open Space of Simi Valley, this abandoned 1930s open-pit limestone mine was once operated by the Tapo Alto Shell & Fertilizer Company. Today, hikers can follow a scenic trail to find fossil-rich geological formations and rusted relics left behind when operations ceased in 1935. The most striking remnant is a remarkably intact P&H Model 206 power shovel, frozen mid-scoop on the hillside.
The story
In 1935, the Tapo Alto Shell & Fertilizer Company abruptly walked away from its open-pit operation in the Santa Susana Mountains, leaving behind a hillside carved into fossilized shell beds and heavy iron machinery. They weren't digging for gold or silver; they were harvesting coquina, a sedimentary rock formed from compressed sea shells that was ground down for agricultural lime and soil conditioner.
When the company folded, nobody bothered to haul the heavy gear down the mountain. The primary relic on Tapo Alto Mountain is a P&H Model 206 power shovel, sitting abandoned on the exposed slope. Decades of weather have rusted the iron to a deep orange crust, but the machine remains remarkably intact—its boom extended and its steel bucket frozen mid-scoop in the exact patch of earth it was digging nearly a century ago.
What it's like
Park along Las Llajas Road and head up the wide canyon floor on foot. Ignore raw phone navigation pins for the destination, which regularly misplace the site. Walk roughly 1.9 miles down Las Llajas Canyon Road until you hit the single-track junction that climbs up toward the ridge. The trail is unshaded, so plan for direct sun, and keep your hands off the power shovel itself—that iron frame is a maze of jagged edges and soft footing.
The move: Hike the scenic Coquina Mine Trail together to photograph the historic, rusted P&H Model 206 power shovel and enjoy panoramic views of the Santa Susana Mountains.
📍 Before you go The mine is located on public parkland within the Marr Ranch Open Space and is legally accessible via hiking trails, but visitors should only view the rusted machinery from a safe distance and avoid climbing on the unstable, sharp metal structures.
- 📍 Coquina Mine
- 💸 Free
- ⚡ Low-key
- 🌗 Outdoors
Where: Coquina Mine, California 93063, USA
Hours: Added 2026-07-20 — confirm current access before you go.
Pair it with
- Grandma Prisbrey's Bottle Village — Follow up industrial ruins in the hills with a visit to Grandma Prisbrey’s hand-built, dump-rescued bottle village down in the valley.
- Bear Canyon Mine — If one set of 1930s mining ruins isn't enough, head northeast into Canyon Country to explore the abandoned shafts of Bear Canyon Mine.
- Concrete ruins of the St. Francis Dam — Pair this abandoned 1930s shovel hike with the massive concrete debris fields left behind by William Mulholland's 1928 dam collapse.
Good to know
Is the hike to Coquina Mine legally accessible?
Yes. The mine sits on public parkland within the Marr Ranch Open Space, and you reach it via established public hiking trails.
How far is the mine from the trailhead?
You'll trek about 1.9 miles along Las Llajas Canyon Road before reaching the single-track trail that branches off to climb toward the mine site.
Can you climb inside the old power shovel?
No. The machine has been decaying since 1935, making the metal sharp, rusted, and structurally unpredictable. Stick to viewing it from the dirt path.
Why is there sea shell rock in the Simi Valley mountains?
The area was once covered by a shallow ocean. Over millions of years, dense beds of marine shells compressed into coquina limestone, which 1930s miners quarried for fertilizer.
Plan a visit & invite your people →
Further reading: modernhiker.com · visitsimivalley.com · hikinggirlwithdog.com · photographyontherun.com
last checked: 2026-07-20