Even though the Horseshoe Mine is in close proximity to the Bridge to Nowhere, nearly all passing hikers do not know of it's existence.
The Horseshoe Mine was nearly lost to history, until rediscovered by Hugh Blanchard. After the workers stopped working the mine, not much was reported on the mine for 50 years. Making it a classic case of forgotten gold mines of the San Gabriels'.
It wasn't until 2006 until a man named Hugh Blanchard did extensive research towards the discovery of the old mine, which has allowed many hikers including myself to discover the place for our own. You can read his entry here.
This is place that many hikers miss because of the fact that the mine is located far away from the Bridge To Nowhere trail. Around the 4 mile mark the trail leaves the valley floor and hikes along the steep canyon walls to meet with the bridge, passing the mine. It should be known that exploring mines is dangerous, therefore this location will not be provided.
When my friends and I went to go search for this place, we had backtracked from the bridge to nowhere (hiking the normal trail backwards) and took a right to hike down a rugged overgrown trail with a sign.
The trail we took gets down to the East Fork River. It's very bushy but easy to navigate.
After reaching the east fork river we looked and looked, and hiked downstream for about 15 minutes. About to give up hope hope we found the mine on the side of canyon walls right before light faded.
We began slightly crouched and head down when entering until the mine opened up to about 6ish feet until we could stand. It was dark and dusty and wet to say the least.
Outside the entrance water was flowing out allowing a most vibrant moss to grow inside.
Many fallen boulders and rocks and collapsed places with many passages. Dangerous.
Most of these old gold mining claims in the San Gabriel Mountains follow the same story. Which begins with hard work and immediate promise to strike it rich. Then after years of work, the resources put in do not match the adequate resources to continue the working, thus leaving the mine abandoned. This mine was worked from 1910 to around the 50's.
The only relic we could find were the old ore cart rails. They line the entire first passage of the mine. After about an hour of exploring we left and hiked back to our car during the night.