As of the 2000 census, there were 873,341 people, 324,565 households, and 224,274 families residing in the county. The population density was 1,762 per square mile (680 /km). (The Census Bureau has since estimated that the population grew to just over 930,000 by 2007.) In 2000, there were 334,632 housing units at an average density of 675 per square mile (261 /km).
The racial makeup of the county was:
In addition, 11.52% of the population was Hispanic or Latino, of any race. (Montgomery County has the largest South American community in the Baltimore-Washington metropolitan area.)
Significant national ethnic groups included people of Irish (8.5%), German (8.1%), English (6.8%) and American (5.0%) ancestry according to Census 2000. The county also has a sizable Jewish population.
There were 324,565 households out of which 35% had children under the age of 18 living with them, 55.2% were married couples living together, 10.5% had a female householder with no husband present, and 30.9% were non-families. 24.4% of all households were made up of individuals, and 7.7% had someone living alone who was 65 years of age or older. The average household size was 2.66 and the average family size was 3.19.
25.4% of the population was under the age of 18, 6.9% from 18 to 24, 32.3% from 25 to 44, 24.2% from 45 to 64, and 11.2% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 92.1 males. For every 100 females age 18 and over, there were 88.1 males.
Montgomery County has the eighth highest household median income in the United States, and the second highest in the state after Howard County according to the 2007 American Community Survey conducted by the U.S. Census Bureau. The median income for a household in the county for 2007 was $89,284 and the median income for a family was $106,093. Males had a median income of $66,415 versus $52,134 for females. The per capita income for the county was $43,073. About 3.3% of families and 4.6% of the population were below the poverty line, including 4.6% of those under age 18 and 4.6% of those age 65 or over.
Since the 1970s, the county has had in place a Moderately Priced Dwelling Unit (MPDU) zoning plan that requires developers to include affordable housing in any new residential developments that they construct in the county. The goal is to create socioeconomically mixed neighborhoods and schools so the rich and poor are not isolated in separate parts of the county. Developers who provide for more than the minimum amount of MPDUs are rewarded with permission to increase the density of their developments, which allows them to build more housing and generate more revenue. Montgomery County was one of the first counties in the U.S. to adopt such a plan, but many other areas have since followed suit.
Montgomery County is approximately bisected north-south by Interstate 270, a connector linking Interstate 70 with Washington. I-270 divides in North Bethesda with its primary roadway connecting to the eastbound Capital Beltway (Interstate 495), and a spur connecting to southbound I-495 as it approaches Northern Virginia. Another spur highway, Interstate 370, connects Interstate 270 with the Shady Grove Metro station.
A fiercely- and long-contested east-west toll freeway, the Intercounty Connector (Maryland Route 200), also known as the ICC, is under construction as of late 2007. The ICC will link Interstate 370 and I-270 with U.S. 29; and Interstate 95 and U.S. 1 in Laurel, Prince George's County.
Roughly paralleling 270 is Maryland Route 355, a surface street known for much of its length as Rockville Pike. In its southern reaches it is known as Wisconsin Avenue, while in the north it is known as Frederick Road, or Frederick Ave in Gaithersburg; in the northern half of Rockville (from Town Center north), it is named Hungerford Drive.
Other major routes include Maryland Route 190 (River Road); Maryland Route 97 (Georgia Avenue); Maryland Route 650 (New Hampshire Avenue), Maryland Route 185 (Connecticut Avenue), Randolph Road/Montrose Road, and Maryland Route 28 (Darnestown Road, Montgomery Avenue and Norbeck Road). U.S. Route 29 parallels the eastern border of the county; first as Georgia Avenue in Silver Spring, then Colesville Road, and thence as Columbia Pike through Burtonsville and into Howard County.
The Montgomery County government has strongly supported the use of automated traffic enforcement on county roads. In 2007 this county became the first jurisdiction in Maryland to introduce automated speed cameras on roads with speed limits up to 35mph, issuing fines of $40 by mail. Red light cameras with fines of $75 are also in use.
Montgomery County operates its own bus public transit system, known as Ride On. Major routes are also covered by WMATA's Metrobus service.
Montgomery County is served by three passenger rail systems.
Amtrak, the U.S. national passenger rail system, operates its Capitol Limited to Rockville, between Washington Union Station and Chicago Union Station.
The Brunswick line of the MARC commuter rail system makes stops at Silver Spring, Kensington, Garrett Park, Rockville, Washington Grove, Gaithersburg, Metropolitan Grove, Germantown, Boyds, Barnesville, and Dickerson, where the line splits into its Frederick and Martinsburg branches.
Both suburban arms of the Red Line of the Washington Metro serve Montgomery County. It follows the CSX right of way to the west, roughly paralleling Route 355 from Friendship Heights to Shady Grove. The eastern side runs between the two tracks of the CSX right of way from Washington Union Station to Silver Spring, and roughly parallels Georgia Avenue, from Silver Spring to Glenmont.
There has been much debate on the construction of two new transitways, both of which are still in the early stages of design. The Purple Line would run "cross-town" connecting nodes in Montgomery and Prince George's Counties near the Beltway; and the Corridor Cities Transitway would provide an extension of the Red Line corridor from Gaithersburg to Germantown and beyond.
The Montgomery County Airpark (FAA GAI, ICAO KGAI), a general aviation facility in Gaithersburg, is the major airport in the county. Davis Airport (FAA Identifier W50), a privately owned airstrip, is located in Laytonsville on Hawkins Creamery Road. Commercial air service is provided at the nearby Ronald Reagan Washington National, Washington Dulles International, and BWI Airports.