The town of Deer Park traces its history back to the 1770s, long before Garrett County was established. The town was part of property owned by Lord Baltimore and was originally surveyed on April 14, 1774. Deer Park saw immense growth during the mid to late 1880s, primarily because of the Baltimore and Ohio Railroad. The Deer Park Hotel, constructed in 1872, served as the focal point for visitors who came to the mountaintop to enjoy the area's scenery and cool temperatures during the summer months. Numerous large cottages were subsequently erected and made available to wealthy visitors. President and Mrs. Grover Cleveland spent the first night of their honeymoon in Deer Park, June 3, 1886. As automobiles became more readily available in the early 1900s, transportation was no longer limited to railroad service, and Deer Park lost its appeal as a vacation destination. The fortunes of the town took a gradual downturn. Fires and demolitions have destroyed many of the fine homes and hotels that once were abundant in the area. Pennington Cottage was listed on the National Register of Historic Places in 1976. Glamorgan was listed in 1984.
As of the census of 2010, there were 399 people, 156 households, and 112 families living in the town. The population density was. There were 175 housing units at an average density of. The racial makeup of the town was 99.5% White and 0.5% African American. Hispanic or Latino of any race were 0.3% of the population. There were 156 households, of which 41.0% had children under the age of 18 living with them, 51.9% were married couplesliving together, 15.4% had a female householder with no husband present, 4.5% had a male householder with no wife present, and 28.2% were non-families. 23.7% of all households were made up of individuals, and 10.3% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 2.99. The median age in the town was 34.9 years. 29.6% of residents were under the age of 18; 6.7% were between the ages of 18 and 24; 27.1% were from 25 to 44; 23.8% were from 45 to 64; and 12.8% were 65 years of age or older. The gender makeup of the town was 47.9% male and 52.1% female.
2000 census
As of the census of 2000, there were 405 people, 161 households, and 112 families living in the town. The population density was 405.7 people per square mile. There were 181 housing units at an average density of 181.3 per square mile. The racial makeup of the town was 97.53% White, and 2.47% from two or more races. There were 161 households, out of which 30.4% had children under the age of 18 living with them, 49.7% were married couples living together, 14.9% had a female householder with no husband present, and 30.4% were non-families. 26.1% of all households were made up of individuals, and 7.5% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.04. In the town, the population was spread out, with 26.2% under the age of 18, 9.4% from 18 to 24, 29.9% from 25 to 44, 21.2% from 45 to 64, and 13.3% who were 65 years of age or older. The median age was 35 years. For every 100 females, there were 97.6 males. For every 100 females age 18 and over, there were 94.2 males. The median income for a household in the town was $26,339, and the median income for a family was $30,000. Males had a median income of $26,875 versus $16,667 for females. The per capita income for the town was $11,302. About 21.2% of families and 24.6% of the population were below the poverty line, including 40.2% of those under age 18 and 18.8% of those age 65 or over.
