The Supplemental Security Income (SSI) program provides income support to needy persons aged 65 or older, blind or disabled adults, and blind or disabled children. Eligibility requirements and federal payment standards are nationally uniform. SSI replaced the former federal/state adult assistance programs in the 50 states and the District of Columbia.
Payments under SSI began in January 1974, with 3.2 million persons receiving federally administered payments. By December 1974, this number had risen to nearly 4 million and remained at about that level until the mid-1980s, then rose steadily, reaching nearly 6 million in 1993 and 7 million by the end of 2004. As of December 2017, the number of recipients was about 8.2 million. Of this total, 4.8 million were between the ages of 18 and 64, 2.2 million were aged 65 or older, and 1.2 million were under age 18.
https://www.ssa.gov/policy/docs/chartbooks/fast_facts/2018/fast_facts18.html#pagei
