State and local protected areas/sites

• Colonial Dorchester State Historic Site
• Edisto River Wildlife Management Area^[6]
• Givhans Ferry State Park (part)
• Middleton Place

Major water bodies

• Ashley River
• Four Hole Swamp
• Edisto River

Adjacent counties

• Bamberg County – west
• Berkeley County – east
• Charleston County – southeast
• Colleton County – southwest
• Orangeburg County – northwest

Major highways

• I-26
• I-95
• US 15
• US 17
• 
  US 17 Alt.
• 
  US 17 Alt. Truck
• US 78
• US 178
• SC 27
• SC 61
• 
  SC 61 Conn.
• SC 165
• SC 453
• SC 642

Major infrastructure

• Summerville Airport

2020 census

As of the 2020 census, there were 161,540 people, 57,768 households, and 41,473 families residing in the county.

2010 census

At the 2010 census, there were 136,555 people, 50,259 households, and 36,850 families living in the county.^[13][11] The population density was 238.2 inhabitants per square mile (92.0/km²). There were 55,186 housing units at an average density of 96.3 units per square mile (37.2 units/km²).^[14] The racial makeup of the county was 67.8% white, 25.8% black or African American, 1.5% Asian, 0.7% American Indian, 0.1% Pacific islander, 1.4% from other races, and 2.6% from two or more races. Those of Hispanic or Latino origin made up 4.4% of the population.^[13] In terms of ancestry,^[15]

Of the 50,259 households, 40.3% had children under the age of 18 living with them, 52.6% were married couples living together, 16.0% had a female householder with no husband present, 26.7% were non-families, and 21.6% of households were made up of individuals. The average household size was 2.68 and the average family size was 3.11. The median age was 35.6 years.^[13]

The median household income was $55,034 and the median family income was $63,847. Males had a median income of $45,659 versus $32,221 for females. The per capita income for the county was $24,497. About 9.0% of families and 11.2% of the population were below the poverty line, including 16.4% of those under age 18 and 9.1% of those age 65 or over.^[16]

2000 census

At the 2000 census, there were 96,413 people, 34,709 households, and 26,309 families living in the county. The population density was 168 people per square mile (65 people/km²). There were 37,237 housing units at an average density of 65 units per square mile (25 units/km²). The racial makeup of the county was 71.05% White, 25.08% Black or African American, 0.73% Native American, 1.13% Asian, 0.07% Pacific Islander, 0.59% from other races, and 1.36% from two or more races. 1.79% of the population were Hispanic or Latino of any race.^[17] Of the 34,709 households 40.00% had children under the age of 18 living with them, 57.20% were married couples living together, 14.60% had a female householder with no husband present, and 24.20% were non-families. 20.20% of households were one person and 6.50% were one person aged 65 or older. The average household size was 2.72 and the average family size was 3.13.

The age distribution was 28.90% under the age of 18, 7.70% from 18 to 24, 31.60% from 25 to 44, 22.60% from 45 to 64, and 9.10% 65 or older. The median age was 35 years. For every 100 females, there were 95.80 males. For every 100 females age 18 and over, there were 91.70 males.

The median household income was $43,316 and the median family income was $50,177. Males had a median income of $35,423 versus $24,405 for females. The per capita income for the county was $18,840. About 7.10% of families and 9.70% of the population were below the poverty line, including 11.40% of those under age 18 and 13.30% of those age 65 or over.

Politics

City

• North Charleston (largest community; partly in Berkeley Charleston counties)

Town

• Harleyville
• Lincolnville (mostly in Charleston County)
• Reevesville
• Ridgeville
• St. George (county seat)
• Summerville (partly in Berkeley and Charleston counties)

Census-designated place

• Ladson (partly in Berkeley County and Charleston County)

Unincorporated communities

• Grover
• Byrds
• Knightsville

Ghost town

• Dorchester