Marshall is situated at latitude 44.47N and longitude -95.78W, with an elevation of above sea level. The city is northeast of Sioux Falls, South Dakota and southwest of Minneapolis. It is in the Central Standard time zone and has the ZIP code 56258. According to the United States Census Bureau, the city has an area of , of which is land and is water. It is in a predominantly rural and agricultural area that was originally an expanse of northern tallgrass prairie. The Redwood River's flood plain begins in Marshall.