It was named for Morgan T. Rich, who settled on the site of the future Wahpeton in 1869.

[3][4] In 2022, strong winds known as a derecho, more than 70 mph, produced 34 tornadoes, including one that passed through Richland County near LeMars.

[5] Richland County lies at the southeastern corner of North Dakota.

The Red River flows northerly along its eastern boundary line on its way to the Hudson Bay.

The Richland County terrain is primarily flat, with rolling hills in the southwest and northwest.

[6] The terrain slopes to the north and east, with its highest point near its SW corner, at 1,220 ft (370 m) ASL.

In only one national election since 1936 has the county selected the Democratic Party candidate (as of 2024).