As an unincorporated area, Potomac's boundaries are not officially defined. Potomac is, however, recognized by the United States Census Bureau as a Census-designated Place, and by the United States Geological Survey as a populated place located at 39°1'22" North, 77°11'11" West (39.022694, -77.186423)1.
According to the United States Census Bureau, the place has a total area of 68.8 km² (26.6 mi²). 65.2 km² (25.2 mi²) of it is land and 3.6 km² (1.4 mi²) of it is water. The total area is 5.20% water.
As of the census of 2000, there are 44,822 people, 15,655 households, and 13,024 families residing in the area. The population density is 687.3/km² (1,780.2/mi²). There are 15,960 housing units at an average density of 244.7/km² (633.9/mi²). The racial makeup of the area is 79.46% White, 3.93% African American, 0.11% Native American, 13.37% Asian, 0.01% Pacific Islander, 0.90% from other races, and 2.22% from two or more races. 5.38% of the population are Hispanic or Latino of any race.
There are 15,655 households out of which 38.4% have children under the age of 18 living with them, 74.8% are married couples living together, 6.6% have a female householder with no husband present, and 16.8% are non-families. 14.0% of all households are made up of individuals and 5.9% have someone living alone who is 65 years of age or older. The average household size is 2.84 and the average family size is 3.10.
In the area, the population is spread out with 26.3% under the age of 18, 4.6% from 18 to 24, 21.3% from 25 to 44, 34.0% from 45 to 64, and 13.8% who are 65 years of age or older. The median age is 44 years. For every 100 females there are 91.7 males. For every 100 females age 18 and over, there are 87.3 males.
The median income for a household in the area is $128,936, and the median income for a family is $142,472. Males have a median income of $100,000 versus $54,428 for females. The per capita income for the area is $64,875. 3.3% of the population and 2.5% of families are below the poverty line. Out of the total people living in poverty, 3.6% are under the age of 18 and 3.6% are 65 or older.
Potomac, MD 20854 is the second-most affluent zip code in the entire United States, coming in second only behind Beverly Hills, California 90210. The television show Beverly Hills 90210 was originally going to be titled Potomac 20854. One of the reasons Potomac is so affluent is that it is located right near Washington D.C Many rich businessmen live in Potomac and commute in to Washington D.C. during the day to work.