Sidney is a city in and the county seat of Richland County, Montana, United States, less than 10 mi (16 km) west of the North Dakota border. The population was 5,191 at the 2010 census. The city lies along the Yellowstone River and is in proximity to the badlands of the Dakotas. Sidney is approximately midway between Glendive, Montana and Williston, North Dakota.
Sidney is located in the northeastern part of the state at 47°42′45″N 104°9′41″W / 47.71250°N 104.16139°W / 47.71250; -104.16139 (47.712519, -104.161486), at an altitude of 1,949 feet (594 m).
According to the United States Census Bureau, the city has a total area of 2.68 square miles (6.94 km), of which, 2.66 square miles (6.89 km) is land and 0.02 square miles (0.05 km) is water.
Sidney is 270 miles (430 km) northeast of Billings, and 190 miles (310 km) south of Regina, Saskatchewan.
Sidney experiences a semi-arid climate (Köppen BSk) with long, cold, dry winters and hot, wetter summers.
As of the census of 2010, there were 5,191 people, 2,304 households, and 1,378 families residing in the city. The population density was 1,951.5 inhabitants per square mile (753.5/km). There were 2,467 housing units at an average density of 927.4 per square mile (358.1/km). The racial makeup of the city was 94.9% White, 0.1% African American, 1.8% Native American, 0.4% Asian, 0.7% from other races, and 2.2% from two or more races. Hispanic or Latino of any race were 3.4% of the population.
There were 2,304 households of which 28.5% had children under the age of 18 living with them, 46.0% were married couples living together, 8.6% had a female householder with no husband present, 5.2% had a male householder with no wife present, and 40.2% were non-families. 33.7% of all households were made up of individuals and 12.9% had someone living alone who was 65 years of age or older. The average household size was 2.24 and the average family size was 2.85.
The median age in the city was 39.3 years. 23.3% of residents were under the age of 18; 8.2% were between the ages of 18 and 24; 24.7% were from 25 to 44; 29% were from 45 to 64; and 14.8% were 65 years of age or older. The gender makeup of the city was 50.6% male and 49.4% female.
As of the census of 2000, there were 4,774 people, 2,006 households, and 1,271 families residing in the city. The population density was 2,125.3 people per square mile (819.2/km²). There were 2,393 housing units at an average density of 1,065.3 per square mile (410.6/km²). The racial makeup of the city was 95.81% White, 0.10% African American, 1.89% Native American, 0.31% Asian, 1.01% from other races, and 0.88% from two or more races. Hispanic or Latino of any race were 2.43% of the population.
There were 2,006 households out of which 31.8% had children under the age of 18 living with them, 49.8% were married couples living together, 9.9% had a female householder with no husband present, and 36.6% were non-families. 33.0% of all households were made up of individuals and 15.3% had someone living alone who was 65 years of age or older. The average household size was 2.33 and the average family size was 2.98.
In the city, the population was spread out with 26.7% under the age of 18, 7.1% from 18 to 24, 26.6% from 25 to 44, 21.8% from 45 to 64, and 18.0% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 92.3 males. For every 100 females age 18 and over, there were 85.8 males.
The median income for a household in the city was $32,109, and the median income for a family was $38,992. Males had a median income of $30,347 versus $18,517 for females. The per capita income for the city was $16,911. About 8.5% of families and 12.7% of the population were below the poverty line, including 17.1% of those under age 18 and 8.7% of those age 65 or over.