Before the twentieth century, there were two leading approaches of the development of American historiography. The earlier one was called Puritan History, and the later one was called Patricain History. The approaches had dominated the development of American historiography for a long time. However, when the century turned, the historical explanation and concepts of Puritan History and Patrician History couldn’t satisfy the new generation historians. Most of them had been to foreign countries and learned the newest theories of history and social science from Europe. After the young generation historians went back to American, they began to criticize outmoded historical concepts and interpretations of Puritan History and Patrician History. To improve American historiography and research methods, they started a movement, which called “The Now History”. There were four key points of the movement: 1.contemporary and modern ages were more important than ancient and medieval ages, 2.history direction was decided by basic structure of society, 3.hisotry interpretations were focused, 4.hisotry should be written from the standpoint of interest in the present. On of them was Charles Austain Beard. He had outstanding achievements in his life. In his book, an Economic Interpretation of the Constitution of the United States, he used economic interpretation to analyze the American Constitution carefully and seriously. In this book, one of the conclusions was the American Constitution was not made by the great majority of Americans, but only by a few people. In addition, the function of the Constitution was to protect private property.