The county is named for George Washington Cass, president of the Northern Pacific Railway from 1872 to 1875.

Cass County is part of the Fargo, ND-Moorhead, MN Metropolitan Statistical Area.

Cass County was defined by action of the Dakota Territory legislature on January 4, 1873, and its organization was effected on October 27 of that year.

The Red River flows northward along the county's east boundary, on its way to Lake Winnipeg and Hudson Bay.

The county's terrain consists of low rolling hills, devoted to agriculture except around developed areas.

[8] Its terrain slopes to the north and east, with its highest point on the southwestern corner at 1,194 ft (364 m) ASL.

Cass County is governed by a board of commissioners elected to four-year terms.

The voters of Cass County have historically tended to vote Republican.

As recently as the 2004 presidential election, George W. Bush carried Cass County with nearly 60 percent of the vote.

Mitt Romney's winning margin in 2012 over Obama in Cass County was 49.9% to 47%, while Donald Trump received 49.3% of votes in 2016, compared to 38.8% for Hillary Clinton and 11.9% for third-party candidates.

In 2018, Democratic Senator Heidi Heitkamp achieved a 14-point lead in Eastern North Dakota, although the state as a whole soundly elected Republican Kevin Cramer.