Doggone Horsethief! Letterbox Hybrid

A little cache near the horsethief canyon dog park in San Dimas. This here's about as western of a town as you can get in these parts. Enjoy yer time here, pardner!

to find the cache:

Look to the south end of the little dog corral;

Midpoint between the corners, find the station for the little poopers;

Immediately south of the poop station, seek, that which is thorny;

Hanging there, like a horse thief, you will find the cache.

Doggone it! Don't be a thief. Leave the stamp in the treasure box alone.