Piasa was once a magnificent rock painting with two horrible monsters on it. This painting is carved on a cliff which is located in Illinois, the United States and overlooking the Mississippi River. Since 2004, authors of New Explanation of Zheng He's discovery of America began to make deep research on Piasa's origin. According to records from France, the United States and China, they find that Piasa is a Rainbow Dragon painted by Zheng He's fleet when they came to North America. More incredibly, His-yang-chi written by Luo Maodeng is the basis for their argument.