The "City Beautiful" movement determined the National Mall of today
In the early 1900s, the brith of urban planning came with the City Beautiful movement. Following the great Columbian Exposition designed by Daniel Burnham in Chicago, Washington D.C. notables created the MacMillan Plan for the National Mall.
The movement promoted beauty not only for its own sake, but also to create civic virtue among city dwellers
Led by the upper middle class concerned with progressive social reform, the movement flourished during the 1890s and 1900s. They believed that beautification including monumental grandeur could promote a harmonious social order that would enhance the quality of life.
(I can't help but pause here to reflect on how our infrastructure molds our societal patterns and behaviors. Ex: Life where I live in Southern California is only possible because of the redirection of water resources from far away. What comes to mind for you?)