Pipestone Quarry on the Coteau des Prairies, 1836–37 oil 19 1/2 x 27 1/4 in. Smithsonian American Art Museum, Gift of Mrs. Joseph Harrison, Jr.   Catlin inevitably attracted controversy. Critics questioned his acute paintings of the torturous Mandan O-kee-pa ceremony because no verification was possible after the Mandan were decimated by smallpox in 1837, soon after Catlin's portrayals. Critics also implied that he exaggerated the details of his trip to the sacred Pipestone Quarry. These issues unfairly tarnished his reputation for years to come, and verification of his paintings and writings came only after his death in 1872. The more Catlin traveled among Plains Indians, the more he became an outspoken advocate for the preservation of their culture. He believed that the Euro-Americans' policies, alcohol, and diseases would wipe out the Indians, the buffalo, and the Great Plains as he knew them. To preserve this splendid world, he advocated that the Great Plains be set aside as a "nation's park."