Pictograph Cave is a 23-acre (93,000 m2) area of three caves (Pictograph, Middle, and Ghost caves) located 5 miles (8 km) south of Billings, Montana, United States.
Excavation of the three caves began in 1937, and they were the site of some of Montana's first professional archeological studies. Over 30,000 artifacts have been identified, with at least 20,000 animal remains recovered from the site. Species range from large mammalian species, including bison (Bos bison) and elk (Cervus elaphus), to various species of herpetiles (reptiles and amphibians) and avies (birds). The presence of these remains result from human predation, processing and consumption as well as non-human (carnivores and raptors) predation and individual species who lived and died in and around the site.
Paintings known as pictographs are still visible in Pictograph Cave, which is the largest of the three caves. The pictographs are thought to be between 200 and 2,100 years old. However their interpretations are still debated over. The oldest pictograph is that of a turtle, radio-carbon dated to be approximately 2,100 years old. These pictographs are paintings of animals, warriors, and even rifles that document the story of the Native Americans of the area for thousands of years.
The site was designated a National Historic Landmark in 1964.(Wikipedia)
"Ghost Cave at Pictograph Cave State Park"