An empirical estimate of how many deaf and hard-of-hearing persons use sign language in the USA was obtained a half-century ago, but no study has measured how many people sign regardless of deafness. This study estimated the number of deaf, hard-of-hearing, and hearing adult signers. Concatenation of the 2010-2018 National Health Interview Surveys was required to provide sufficient sample size. Unadjusted and age-by-sex-adjusted sign language use prevalence across the range of hearing acuity was estimated. Adult sign language use was substantial (2.80%), with its rate of use greater for women than men and younger adults than older adults. As a group, deaf respondents had a far higher rate of sign language use than any other hearing acuity group. This study provides the first empirical estimate of adult sign language use generally, and the first update of any sign language use estimate in a half-century.