Cobb, along with several other counties in the same bill, was created December 3, 1832 by the Georgia General Assembly from the huge Cherokee "county" territory — land northwest of the Chattahoochee River which the state confiscated from the Cherokee Nation and redistributed to settlers via lottery, following the passage of the federal Indian Removal Act.
As of the 2000 census, the population is 607,751. The county's population has continued to grow. The 2008 estimate from the U.S. Census Bureau was 698,158 people. The county is part of the original and core (five-county) Atlanta metropolitan area, which is included in the Atlanta–Sandy Springs–Marietta, Georgia metropolitan statistical area.
The U.S. Census Bureau ranks Cobb County as the most-educated in the State of Georgia and 15th among all counties in the United States. It is consistently ranked among top 100 wealthiest counties in the United States.
As of 2006, there were 679,325 people, 248,303 households, and 169,178 families residing in the county. The population density was 1,998 people per square mile (763/km²). There were 261,659 housing units at an average density of 770 per square mile (301/km²). The racial makeup of the county in 2006 was 56.0% White, 29.6% Black, 0.5% Native American, 4.1% Asian, 0.0% Pacific Islander, 8.8% from other races, and 1.4% from two or more races. 11.1% of the population were Hispanic or Latino of any race.
There were 248,303 households out of which 35.80% had children under the age of 18 living with them, 54.30% were married couples living together, 10.70% had a female householder with no husband present, and 31.20% were non-families. 23.20% of all households were made up of individuals and 4.10% had someone living alone who was 65 years of age or older. The average household size was 2.71 and the average family size was 3.25.
In the county the population was spread out with 26.10% under the age of 18, 9.00% from 18 to 24, 36.50% from 25 to 44, 21.50% from 45 to 64, and 6.90% who were 65 years of age or older. The median age was 33 years. For every 100 females there were 98.50 males. For every 100 females age 18 and over, there were 95.90 males.
As of 2007, the mean income for a household in the county was $85,751, and the mean income for a family was $101,065. Males had a median income of $51,745 versus $42,509 for females. The per capita income for the county was $32,740. About 6.0% of families and 9.4% of the population were below the poverty line, including 9.1% of those under age 18 and 7.8% of those age 65 or over.