A small rock carving along the Green River in Whirlpool Canyon, now within Dinosaur National Monument in Moffat County, Colorado, preserves the inscription “DJ 1838” left by French-American trapper Denis Julien. Julien was among the few Europeans known to have traveled this area in the 1830s and seems to have regularly marked locations along the Green and Colorado rivers, leaving at least eight inscriptions. Set about 5 feet above normal water level but below flood level, this carving is closely tied to river travel through remote canyon country. It survives as a rare trace of the early fur-trade era in the upper Colorado River basin and was listed on the National Register of Historic Places in 1986.