Redlining is the systematic practice of denying services to people in specific areas, generally along racial lines. This happened nationwide, but has had a large impact on Oakland over the years. The specific practice called "redlining" began with the National Housing Act of 1934, 1 but segregation and discrimination had of course existed long before that in Oakland.
In particular, people living in red areas of the map usually couldn't get home loans, and through restrictive covenants and direct discrimination, people of color often were not allowed to live anywhere else. This resulted in more white homeowners (even for comparable incomes), and "urban decay" in red areas. Business owners were also denied loans.
Links and References
- Google Maps version of 1937 map joshbegley.com
- The Racist Housing Police That Made Your Neighborhood by Alexis Madrigal The Atlantic May 22, 2014