Washington County is located in the western part of the U.S. state of Maryland. As of the 2010 census, the population was 147,430. Its county seat is Hagerstown. Washington County was the first county in the United States to be named for the Revolutionary War general (and later President) George Washington. Washington County is one of three Maryland counties recognized by the Appalachian Regional Commission as being part of Appalachia.
According to the U.S. Census Bureau, the county has a total area of 467 square miles (1,210 km), of which 458 square miles (1,190 km) is land and 9.6 square miles (25 km) (2.0%) is water.
Washington County is located in the Appalachian Mountains, stretching from the Ridge-and-Valley Country in the west to South Mountain in the east, which is an extension of the Blue Ridge. Much of the county lies in the broad Hagerstown Valley between these two zones; the valley is part of the Great Appalachian Valley that continues southward into Virginia and West Virginia as the Shenandoah Valley and northward into Pennsylvania as the Cumberland Valley.
The county is bordered to the north by the Mason–Dixon line with Pennsylvania, to the south by the Potomac River and the states of Virginia and West Virginia, to the west by Sideling Hill Creek and Allegany County, Maryland, and to the east by Frederick County and South Mountain.
As of the census of 2010, there were 147,430 people, 49,726 households, and 34,112 families residing in the county. The population density was 315 people per square mile (111/km²). There were 52,972 housing units at an average density of 116 per square mile (45/km²). The racial makeup of the county was 89.71% White or Caucasian, 7.77% Black or African American, 0.18% Native American, 0.80% Asian, 0.04% Pacific Islander, 0.46% from other races, and 1.04% from two or more races. 1.19% of the population were Hispanic or Latino of any race, 32.1% identified as being of German ancestry, 21.4% American, 8.8% Irish, and 8.4% English ancestry.
There were 49,726 households out of which 31.30% had children under the age of 18 living with them, 54.00% were married couples living together, 10.70% had a female householder with no husband present, and 31.40% were non-families. 26.00% of all households were made up of individuals and 11.10% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 2.96.
In the county, the population was spread out with 23.40% under the age of 18, 8.10% from 18 to 24, 31.30% from 25 to 44, 23.00% from 45 to 64, and 14.20% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 104.50 males. For every 100 females age 18 and over, there were 104.00 males.
As of the 2010 United States Census, there were 147,430 people, 55,687 households, and 37,506 families residing in the county. The population density was 322.1 inhabitants per square mile (124.4/km). There were 60,814 housing units at an average density of 132.8 per square mile (51.3/km). The racial makeup of the county was 85.1% white, 9.6% black or African American, 1.4% Asian, 0.2% American Indian, 1.1% from other races, and 2.6% from two or more races. Those of Hispanic or Latino origin made up 3.5% of the population. In terms of ancestry, 31.7% were German, 14.1% were Irish, 9.8% were English, 8.5% were American, and 5.1% were Italian.
Of the 55,687 households, 32.4% had children under the age of 18 living with them, 50.6% were married couples living together, 12.0% had a female householder with no husband present, 32.6% were non-families, and 26.6% of all households were made up of individuals. The average household size was 2.50 and the average family size was 3.01. The median age was 39.7 years.
The median income for a household in the county was $52,994 and the median income for a family was $65,811. Males had a median income of $47,622 versus $34,225 for females. The per capita income for the county was $26,588. About 7.7% of families and 10.4% of the population were below the poverty line, including 14.1% of those under age 18 and 8.8% of those age 65 or over.