PEOPLE OVERVIEW : The 2016 Milbank, South Dakota, population is 3,192. There are 1,157 people per square mile (population density). Family in Milbank, South Dakota. The median age is 43.9. The US median is 37.4. 58.09% of people in Milbank, South Dakota, are married. 8.71% are divorced. The average household size is 2.12 people. 28.40% of people are married, with children. 9.13% have children, but are single. Race in Milbank, South Dakota. 91.78% of people are white, 0.70% are black, 0.00% are asian, 2.48% are native american, and 0.00% claim 'Other'. 4.77% of the people in Milbank, South Dakota, claim hispanic ethnicity (meaning 95.23% are non-hispanic).