Bollinger County is located in the southeastern part of Missouri, about 90 miles south of St. Louis and 25 miles west of the Mississippi River. It is bordered on the east by Cape Girardeau County, on the south by Stoddard County, on the west by Wayne and Madison Counties, and on the north by Perry County. The total area of the county is 397,235 acres, or about 620 square miles.
Bollinger County has two distinct physio-graphic regions within its borders. The Salem Plateau, which covers most of the county, is an extensive land region made of Ordovician age rocks that surrounds the St. Francois Mountains. In Bollinger County, these rocks are mostly cherry dolostone with some thin inter-bedded sandstone. A thin loose deposit covers the broader ridge tops. The plateau is highly dissected by numerous streams forming interconnecting ridges and steep hill slopes.