City of Eureka, South Dakota

Eureka is located at 45°46'9" North, 99°37'8" West (45.769167, -99.618889).

According to the United States Census Bureau, the city has a total area of 1.00 mi² (2.59 km²). 0.93 mi² (2.42 km²) of it is land and 0.07 mi² (0.17 km²) of it is covered by water. The total area is 6.70% water.

Eureka is located in the Central Standard Time (CST) timezone, GMT-06:00. It observes Daylight Saving Time (DST).