Groton is a city in southeastern Brown County, South Dakota, United States.

[8] According to the United States Census Bureau, the city has a total area of 1.75 square miles (4.53 km2), all land.

There were 630 housing units at an average density of 360.0 per square mile (139.0/km2).

30.4% of all households were made up of individuals, and 15.4% had someone living alone who was 65 years of age or older.

There were 581 housing units at an average density of 341.3 per square mile (131.8/km2).

27.5% of all households were made up of individuals, and 14.7% had someone living alone who was 65 years of age or older.