Question: The county that Doris Beck was the first woman to serve as a Mayor of had a population of what in 2010?
Sentence (from "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.
Relevant evidence: Yes