Yesterday, apropos of Paul Ryan’s remarks on “inner-city poverty” and a culture that “doesn’t value work,” I wrote about the policy that went into building our inner-cities and depriving whole communities of wealth and opportunity. Likewise, at MSNBC, Ned Resnikoff wrote an excellent piece on the wide income and wealth disparities between blacks and whites. “ In 1984,” he writes, “the white-to-black wealth ratio was 12-to–1…But over the next 14 years the wealth gap began to grow once again, until it had skyrocketed up to 19-to–1 in 2009.”

A large part of this, he explains, has everything to do with housing discrimination:

Disparities in homeownership are a major driver of the racial wealth gap, according to a recent study from Brandeis University. According to the authors of the report, “redlining [a form of discrimination in banking or insurance practices], discriminatory mortgage-lending practices, lack of access to credit, and lower incomes have blocked the homeownership path for African-Americans while creating and reinforcing communities segregated by race.”

In my earlier piece, I alluded to these policies and practices, but didn’t describe them. But it’s worth taking the time to do exactly that, given the extent to which they were a huge influence on the housing landscape of the United States, and key to creating the ghettos and housing projects that litter our inner-cities. Obviously, this won’t be comprehensive, so consider it an introduction to these issues.

Redlining is the practice of denying key services (like home loans and insurance) or increasing their costs for residents in a defined geographical area. In theory, this could be used against anyone. In reality, it was almost exclusively a tool to force blacks (and other minorities) into particular geographic areas. The practice began with the National Housing Act of 1934, which established the Federal Housing Administration, as well as the Federal Home Loan Bank Board. It was this agency which created “residential security maps” for several cities to determine the safety of real estate investments in selected areas.

You should already see where this is going: Existing black neighborhoods were lined as unsafe, and thus ineligible for financing. For prospective property owner, this was terrible: Absent cash on hand, there was no way to afford a home or a business in your area. What’s more, blacks were all but barred from entering white neighborhoods, if not by restrictive racial covenants (which forbid property sales to African Americans and other minorities) then by violence and intimidation. In Chicago, for instance, anti-black riots were a regular part of public life....