When President Franklin Roosevelt and the U.S. Congress created Social Security in 1935, they did not formally exclude any Black Americans because of their race, but they did create a significant racial disparity by restricting eligibility to service and manufacturing workers.
In 1930, 65 percent of Black Americans worked as domestic or farmworkers. In other words, because the program did not cover those occupations, only about one-third of Black workers qualified for Social Security. While Black workers represented 11 percent of the workforce, they represented 23 percent of all workers who were not covered.
There is considerable debate over why this was. Some researchers say it was the racism of the Southern congressmen whom President Roosevelt relied on to push his program through Congress. Others say it simply wasn’t feasible to collect payroll taxes from domestic and farm workers at the time because so many of them were still paid in cash. (For more details, head on over to this SSA Bulletin article.)
But President Roosevelt believed Social Security needed to be universal. Just three years after the program was created, he announced plans to expand it. World War II changed those plans, so it wasn’t until 1950 that Congress extended coverage to domestic and farm workers.
There are many other racial disparities that exist in the program today, and there are many policy ideas to reduce them. For more info on this, the Urban Institute has a helpful paper here.