This paper used Social Security Administration program data from 2005 to 2019 to examine national- and state-level changes in the number of new adult supplemental security income (SSI) awardees on the autism spectrum relative to awardees with intellectual disability and other mental health disorders. We identified three main findings: the number of autistic awards increased between 2005 and 2019 when awards for all other mental health disorders declined; roughly nine out of every 10 autistic adult awardees were between ages 18-25 years; there was variation in the growth of autistic awards across states. These findings support the need to consider geographic and age differences in SSI program participation among autistic adults and determine the underlying causes.