The county that Doris Beck was the first woman to serve as a Mayor of had a population of what in 2010?
Doris Beck: Doris Lew Beck (born 1929) is an American Democratic Party politician who was the first woman to serve as Mayor of Livingston, New Jersey, and the first woman to serve as a Mayor in Essex County, New Jersey. Essex County, New Jersey:  As of the 2016 Census estimate, the county's population was 796,914, making it the state's third-most populous county, an increase of 1.7% from the 2010 United States Census, when its population was enumerated at 783,969, in turn a decrease of 1.2% (9,664 fewer residents) from the 793,633 enumerated in the 2000 Census.
783,969