[2] Fillmore County is included in the Rochester metropolitan area.

[4] Fillmore County was an early destination for Euro-American settlement following the United States' 1851 treaties with the Dakota nations.

Willow Creek also drains a portion of the lower county, discharging into the Root at Preston.

The Upper Iowa River flows eastward, mostly in adjoining Iowa counties, but briefly enters Fillmore County near the midpoint of its southern border.

The county's terrain consists of rolling hills, carved by gullies and drainages, with the available area dedicated to agriculture.

[6] The terrain slopes to the east; its highest point is on the lower western border, at 1,378 ft (420 m) ASL.

28.30% of all households were made up of individuals, and 7.32% had someone living alone who was 65 years of age or older.

Since 2016, Fillmore County has shifted rightward and has voted for the Republican nominee by more than 20% each time.