Sully County, South Dakota Cities (2025)

2 cities

City
Rank
2025 Pop. ↓
2020 Pop.
Change
Density
Area (mi²)
Type
Onida1654664-0.3%9730.67 City
Agar273671.39%3560.20 Town

Sully County Cities Summary

Largest City

Onida is the largest city in Sully County, with a population of 654.

Smallest City

Agar is the smallest city in Sully County.

10 Largest Cities

There are 2 cities in Sully County, South Dakota.