Against the soft, organic edges of the Las Mariposas hills, a human-made road carved out for the rail route appears like a sharply engraved line. Carleton Watkins photographed many images of Las Mariposas, the mineral-rich estate of John C. Frémont, former Republican presidential candidate and United States senator. As the owners of a gold mine, the Frémonts–with whom Watkins maintained a close relationship–were among the wealthiest and most influential people in California. On the way to and from the Frémonts' gold mine, Watkins made at least six exposures. This study, surely made on his return late in the day, benefits from the afternoon sun.