According to the 2010 census, what was the population of the county which headquarters the DeKalb County School District?
DeKalb County School District: The DeKalb County School District (DCSD) is a school district headquartered at 1701 Mountain Industrial Boulevard in the City of Tucker, DeKalb County, Georgia, United States. DeKalb County, Georgia:  As of the 2010 census, the population was 691,893, making it Georgia's fourth-most populous county.
691,893