The original Social Security Act of 1935 did not extend coverage to state and local workers.  Beginning in the 1950’s, the law was changed to allow states and local governments to opt in to coverage.  Until April of 1983, state governments could opt out of Social Security entirely on behalf of their public employees.  In 1983, new legislation banned state governments from opting their employees out of Social Security once they accepted coverage (i.e., once a state opted in, it could never again opt out).