Local archival resources include the State Historical Society of Missouri (which maintains an excellent collection of digitized maps), the Research Center of the Missouri History Museum, and the St. Louis collections at Washington University Special Collections (including the papers of the planning firm Harland Bartholomew and Associates).
The conditions faced by African Americans in St. Louis County is well-documented in the January 1970 Hearings of the United States Commission on Civil Rights (USCCR). A full transcript of the 1970 Hearings is available via the Hathi Trust. The evidence and testimony collected there also features in the USCCR's 1974 report Equal Opportunity in Suburbia (also available from Hathi).
The logic and priorities of urban redevelopment in St. Louis County are laid out in the Elmwood Park Urban Renewal Plan (1962); the copy posted here is from the Brooks v LCRA case file at the Missouri State archives.
The conditions and circumstances surrounding the death of Micheal Brown, particularly the pattern of predatory policing by St. Louis County municipalities, is documented by the Department of Justice's Investigation of the Ferguson Police Department (2015); by the Ferguson Commission's Forward Through Ferguson report (October 2015); and by the ongoing work of Arch City Defenders (see especially their 2014 Municipal Courts White Paper); Better Together St. Louis (see especially their studies of the costs of fragmentation and their excellent data library); and the East-West Gateway Council of Governments (especially their Where We Stand reports).
Citizen Brown draws extensively on the work of St. Louis-based journalists; see especially the work of Sylvester Brown, Clark Randall, Jeannette Cooperman, D.J. Wilson, and Mary Delach Leonard. See also the inestimable reporting of Nicole Hannah-Jones--especially "School Segregation, the Continuing Tragedy of Ferguson" (ProPublica, 2014), and "The Problem We All Live With" (This American Life, 2015).