James City County straddles two major watersheds, the James River Watershed and the York River Watershed. (Both are subwatersheds of the Chesapeake Bay watershed, which stretches from Pennsylvania to Virginia). Within the James River and York watersheds are eleven subwatersheds - Diascund Creek, Ware Creek, Yarmouth Creek, Gordon Creek, Powhatan Creek, Mill Creek, College Creek, James River, York River, Skiffe's Creek and Chickahominy River. According to the U.S. Census Bureau, the county has a total area of 180 mi˛ (465 km˛), of which 143 mi˛ (370 km˛) is land, and 37 mi˛ (95 km˛, or 20.47%) is water.

There were 48,102 people, 19,003 households, and 13,986 families residing in the county according to the 2000 census[2], . The population density was 337/mi˛ (130/km˛). There were 20,772 housing units at an average density of 145/mi˛ (56/km˛). The racial makeup of the county was 82.05% White, 14.37% Black or African American, 0.28% Native American, 1.46% Asian, 0.05% Pacific Islander, 0.44% from other races, and 1.36% from two or more races. 1.70% of the population were Hispanic or Latino of any race.

The median income for a household in the county was $55,594, and the median income for a family was $66,171. Males had a median income of $43,339 versus $27,016 for females. The per capita income for the county was $29,256. 6.40% of the population and 4.10% of families were below the poverty line. Out of the total people living in poverty, 7.30% are under the age of 18 and 4.80% are 65 or older.

Neighboring areas include the following: Gloucester County, York County, Williamsburg city, Newport News city, Charles City County, and New Kent County. The cities and towns in this county are Croaker, Diascund, Five Forks, Grove, Indigo Park, Jamestown, Kingspoint, Kingsmill, Lightfoot, Norge, and Toano.