19世纪中叶到20世纪20年代,美国的城镇化以集聚城镇化为主,中心城市空间向外拓展,周围地区纳入城市范畴。20世纪20年代城镇化进入郊区化扩散阶段,郊区独立建设的城市繁荣起来。20世纪20至30年代,资本主义世界经济危机使人们充分认识到放任自由的市场经济的弊端,凯恩斯 From the mid-19th century to the 1920s, the urbanization in the United States focused on urbanization and the central urban space expanded outward and the surrounding areas were included in urban areas. The urbanization of the 1920s entered the stage of suburbanization and diffusion, and the cities in the suburbs that were independently built prospered. From the 1920s to the 1930s, the economic crisis in the capitalist world fully recognized the drawbacks of the market economy that laissez-faire liberalization. Keynes