Reliance is located at (43.878490, −99.601138).
According to the United States Census Bureau, the town has a total area of 1.1 square miles (3.0 km²), of which, 1.1 square miles (2.8 km²) of it is land and 0.1 square miles (0.1 km²) of it (4.39%) is water.
There were 84 households out of which 35.7% had children under the age of 18 living with them, 47.6% were married couples living together, 10.7% had a female householder with no husband present, and 35.7% were non-families. 32.1% of all households were made up of individuals and 11.9% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 3.11.
In the town the population was spread out with 28.6% under the age of 18, 9.2% from 18 to 24, 25.2% from 25 to 44, 25.2% from 45 to 64, and 11.7% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 100.0 males. For every 100 females age 18 and over, there were 101.4 males.
The median income for a household in the town was $30,833, and the median income for a family was $35,417. Males had a median income of $22,361 versus $21,875 for females. The per capita income for the town was $14,141. About 4.1% of families and 11.2% of the population were below the poverty line, including 9.2% of those under the age of eighteen and 24.0% of those sixty five or over.