An OSTA marker is at Bonita and Walnut in San Dimas, CA and displayed about 4 miles north of the official NPS trail route. The Link can be access here
This plaque commemorates the 1200-mile Old Spanish Trail, an historic pack trail from Santa Fe to Los Angeles. This trail was used by Native Americans, explorers, trappers, immigrants, and Mexican traders who brought woolen goods from New Mexico in exchange for highly prized California mules and horses. In active use between 1829 and 1848, the portion passing through San Dimas became known as the “Upper San Bernardino Road” and was later used by wagons and stagecoaches.