During the first half of the twentieth century Realtors tried to link development of respectable suburban communities with attempts to create a respectable real estate profession. Beginning in 1908, Realtors from around the country sought to formalize their professional networks into a new organization that would allow them to legitimize real estate practice. This group, The National Association of Real Estate Boards, became a gatekeeper for the emerging "profession." Residential developers quickly rose to form a powerful voice within the organization. With their leadership, NAREB established a hierarchy of property value with exclusionary, planned suburbs at the top.
Even as developers tried to standardize both property value and the best methods of residential exclusion through the national organization, firms still had to work out who belonged in the course of their local daily operations. When employees tried to heed NAREB principles, they had to make sense of national debates with their local understandings of who should live in planned suburbs. The resulting tensions between top-down standards and local implementation led to the creation of flexible formulas for exclusion that included and also extended beyond race.