For 2019, it is no longer legal to ask for salary history in California. Applicants may volunteer it and prospective employers may ask for the salary the applicant is looking for, but not past salary, either of the applicant or reference checks.
https://www.mass.gov/service-details/learn-more-details-abou...
https://www.lawandtheworkplace.com/2018/05/connecticut-enact...