It is the only "Germantown, Maryland" recognized by the United States Postal Service, although there are technically three others, one each in Anne Arundel County, Baltimore County, and Worcester County. It has the assigned ZIP Codes of 20874 and 20876 for delivery and 20875 for post office boxes only..
On April 20, 1865, George Atzerodt, a co-conspirator in the Abraham Lincoln assassination was captured in Germantown. He was assigned by John Wilkes Booth to assassinate Vice President Andrew Johnson, but lost his nerve and fled Washington, D.C., on the night of the Lincoln assassination. He was captured at his cousin Hartman Richter's farm in Germantown. Atzerodt was hanged on July 7, 1865 along with Mary Surratt, Lewis Powell, and David Herold in Washington, D.C. Since about 1980, Germantown has experienced great growth, both in townhomes and single-family dwellings, and an urbanized towncenter has been built.
Germantown is located at .
According to the United States Census Bureau, the community has a total area of 10.8 square miles (28.0 km²), of which, 10.8 square miles (27.9 km²) of it is land and 0.1 square miles (0.1 km²) of it (0.46%) is water.
There were 20,893 households out of which 41.2% had children under the age of 18 living with them, 49.8% were married couples living together, 13.7% had a female householder with no husband present, and 32.4% were non-families. 23.5% of all households were made up of individuals and 1.8% had someone living alone who was 65 years of age or older. The average household size was 2.65 and the average family size was 3.19.
In the area, the population was spread out with 28.9% under the age of 18, 7.7% from 18 to 24, 43.0% from 25 to 44, 17.3% from 45 to 64, and 3.1% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 94.9 males. For every 100 females age 18 and over, there were 90.6 males.
The median income for a household in the area was $62,431, and the median income for a family was $67,204. Males had a median income of $46,039 versus $37,237 for females. The per capita income for the area was $26,709. 4.6% of the population and 3.5% of families were below the poverty line. Out of the total people living in poverty, 5.9% are under the age of 18 and 9.9% are 65 or older. The largest families range from 8-12 people.
The Montgomery County public bus system Ride On, serves Germantown with approximately 20 bus routes, and operates a major transit hub at Germantown Transit Center. Also, the Corridor Cities Transitway, a proposed light rail system which will, when completed, connect the terminal of the Washington Metro Red Line at Shady Grove Station near Gaithersburg to Germantown and continue on to Clarksburg, further north.