Despite widespread support for government policies aimed at improving workplace retirement plans, nearly half of wage and salary workers in the U.S. still lack coverage. The lack of employer-sponsored pensions or other workplace retirement saving plans has led to state-level government initiatives aimed at expanding coverage to workers whose employers do not offer such plans. Designing and implementing efforts to broaden workplace retirement plan coverage requires understanding what types of workers lack coverage, in terms of both demographic characteristics and across US states. However, available data on retirement plan coverage is limited, and developing an accurate picture of the current state of retirement plan coverage requires reconciling and benchmarking multiple data sources. This paper describes a method for estimating current workplace retirement plan coverage rates by age, race and ethnicity, education, gender, employer size, and earnings levels across U.S. states using data from the Current Population Survey, IRS Statistics of Income, and Survey of Consumer Finances.