Just next to the mission at San Juan Bautista is what's claimed to be the original route of El Camino Real, the mission route between Los Angeles and San Francisco. Standard Californian belief is that US 101 mostly follows the route of El Camino Real (except in Silicon Valley where it's California 82), but US 101 bypasses the San Benito County town. Since the original route connected most of the missions in the state, it's likely the original road went by here.