Mound City is located at 37°5'6" North, 89°9'43" West (37.085000, -89.162222).
According to the United States Census Bureau, the city has a total area of 0.76 mi2 (1.97 km2). 0.71 mi2 (1.84 km2) of it is land and 0.05 mi2 (0.13 km2) of it is covered by water. The total area is 6.54% water.
Mound City is located in the Central Standard Time (CST) timezone, GMT-06:00. It observes Daylight Saving Time (DST).