Although they bear the same name, Cavalier is not located in nearby Cavalier County. The Tongue River flows past Cavalier and Cavalier Air Force Station is located near the city.
As of the census of 2000, there were 1,537 people, 679 households, and 399 families residing in the city. The population density was 1,938.1 people per square mile (751.2/km²). There were 750 housing units at an average density of 945.7/sq mi (366.6/km²). The racial makeup of the city was 94.27% White, 0.46% African American, 1.04% Native American, 0.52% Asian, 2.08% from other races, and 1.63% from two or more races. Hispanic or Latino of any race were 4.29% of the population.
There were 679 households out of which 26.7% had children under the age of 18 living with them, 50.4% were married couples living together, 6.3% had a female householder with no husband present, and 41.1% were non-families. 38.4% of all households were made up of individuals and 21.8% had someone living alone who was 65 years of age or older. The average household size was 2.17 and the average family size was 2.92.
In the city the population was spread out with 22.8% under the age of 18, 7.2% from 18 to 24, 24.3% from 25 to 44, 21.0% from 45 to 64, and 24.8% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 88.8 males. For every 100 females age 18 and over, there were 85.8 males.
The median income for a household in the city was $35,667, and the median income for a family was $48,450. Males had a median income of $30,313 versus $21,548 for females. The per capita income for the city was $19,586. About 7.8% of families and 9.3% of the population were below the poverty line, including 7.0% of those under age 18 and 9.9% of those age 65 or over.
Based on data from the 2000 Census, 6.8% of Cavalier's population is of Icelandic ancestry, making Cavalier the city with the highest proportion of Icelandic residents in the United States.