Big Bend National Park, the Castolon area's history is of farming, military activity during the Mexican Revolution, and frontier trading post. The park's website has a brief interesting history online, here.
Today the park's Cottonwood Campground sits in land that used to be a farmer's field, the La Harmonia Compnay Store is still open (though it caters to visitors, not ranchers or farmers), and there are exhibits and frequently interpretive activities in the area that help tell the area's story.
Most visitors to the park visit Santa Elena Canyon for the short, spectacular hike. While you're there, plan extra time to poke around and explore the history of this important trading post, too!