According to the population data for the ZIP code 21871 in Fairmount, Maryland, the area has experienced fluctuations in population and population density over the past decade. The population peaked in 2012 at 5,706 and has since declined to 4,318 in 2022. Correspondingly, the population density has decreased from a high of 90.11 people per square mile in 2012 to 68.19 people per square mile in 2022.

Given the ZIP code's size of 63.32 square miles and the 2022 population density of 68.19 people per square mile, the area can be classified as rural. Rural areas are characterized by low population densities, typically between 50 and 500 people per square mile, and feature larger living spaces, ranging from 1 to 5 acres per household. The lifestyle in rural areas is often community-oriented, centered around local schools and small businesses, with activities such as hobby farming, horse ownership, and significant outdoor activities.

The estimated number of housing units corresponding to the 2022 population is 1,654, based on the national average household size of 2.61 people per household. This suggests that the area has a relatively low housing density, consistent with its rural classification.