As of the census of 2000, there were 695,454 people, 273,416 households, and 174,986 families residing in the county. The population density was 1,322 people per square mile (510/km²). There were 292,780 housing units at an average density of 556 per square mile (215/km²). The racial makeup of the county was 64.02% White, 27.87% Black or African American, 0.35% Native American, 3.15% Asian, 0.05% Pacific Islander, 3.01% from other races, and 1.55% from two or more races. 6.45% of the population were Hispanic or Latino of any race .
There were 273,416 households out of which 32.10% had children under the age of 18 living with them, 47.70% were married couples living together, 12.40% had a female householder with no husband present, and 36.00% were non-families. 27.60% of all households were made up of individuals and 5.90% had someone living alone who was 65 years of age or older. The average household size was 2.49 and the average family size was 3.06.
In the county the population was spread out with 25.10% under the age of 18, 9.70% from 18 to 24, 36.40% from 25 to 44, 20.30% from 45 to 64, and 8.60% who were 65 years of age or older. The median age was 33 years. For every 100 females there were 96.50 males. For every 100 females age 18 and over, there were 93.60 males.
The median income for a household in the county was $50,579, and the median income for a family was $60,608. Males had a median income of $40,934 versus $30,100 for females. The per capita income for the county was $27,352. About 6.60% of families and 9.20% of the population were below the poverty line, including 11.50% of those under age 18 and 9.30% of those age 65 or over.
The county's primary commercial aviation airport is Charlotte Douglas International Airport in Charlotte.
With twenty-five freight trains a day, Mecklenburg is a freight railroad transportation center, largely due to its place on the NS main line between Washington and Atlanta and the large volumes of freight moving in and out of the county via truck.
Mecklenburg County is served daily by three Amtrak routes.
The Crescent train connects Charlotte with New York, Philadelphia, Baltimore, Washington, Charlottesville, and Greensboro to the north, and Atlanta, Birmingham and New Orleans to the south.
The Carolinian train connects Charlotte with New York, Philadelphia, Baltimore, Washington, Richmond, Raleigh, Durham and Greensboro.
The Piedmont train connects Charlotte with Raleigh, Durham and Greensboro.
The Amtrak station is located at 1914 North Tryon Street.
A new centralized multimodial train station, Gateway Station, is currently under construction. It is expected to house the future LYNX Purple Line, the new Greyhound bus station, and the Crescent line that passes through Uptown Charlotte.
Mecklenburg County is also the proposed southern terminus for the initial segment of the Southeast High Speed Rail Corridor operating between Charlotte and Washington, D.C. Currently in conceptual design, the SEHSR would eventually run from Washington D.C. to Macon, Georgia.
Light rail service in Mecklennburg County is provided by LYNX Rapid Transit Services. Currently a 9.6-mile (15.4 km) line running from Uptown to Pineville, build-out is expected to be complete by 2034.
Charlotte Area Transit System (CATS) bus service serves all of Mecklenburg County, including Charlotte, and the townships of Davidson, Huntersville, Cornelius, Matthews, Pineville, and Mint Hill.
The vintage Charlotte Trolley also operates in partnership with CATS.
Mecklenburg's manufacturing base, its central location on the Eastern Seaboard and the intersection of two major interstates in the county have made it a hub for the trucking industry.