Charles County is a county located in the U.S. state of Maryland. As of the 2020 census, the population was 166,617. The county seat is La Plata. The county was named for Charles Calvert, third Baron Baltimore. Charles County is part of the Washington metropolitan area and the Southern Maryland region. With a median household income of $103,678, Charles County is the 39th wealthiest county in the United States, and the highest-income county in the United States with a Black-majority population.