- Marshall County, Minnesota has 1,775.1 square miles of land area and is the 10th largest county in Minnesota by total area. Marshall County, Minnesota is bordered by Polk County, Minnesota, Roseau County, Minnesota, Beltrami County, Minnesota, Walsh County, North Dakota, Grand Forks County, North Dakota, Pembina County, North Dakota, Pennington County, Minnesota, and Kittson County, Minnesota.