Some present-day highways, roads, and railroad grades follow the old trails and oxen-cart paths made by Native Americans and the first white settlers that traveled through Otter Tail County.
Interstate 94 from St. Cloud closely follows an old oxen-cart trail that connected with the old Red River Trail. State and Federal highways include Interstate 94, U.S. Highways 10 and 59, and Minnesota Highways 210, 108, 29, and 78. Interstate 94 crosses the southwest corner of the county and serves Fergus Falls. U.S. Highway 10 crosses the northeast corner of the county and passes through the cities of Bluffton, New York Mills, and Perham. U.S. Highway 59 is a north-south route through Fergus Falls that heads north to Canada.
Minnesota Highway 210 crosses from east to west across the southern half of the county and serves the communities of Fergus Falls, Battle Lake, and Henning. Minnesota Highway 29 extends from the city of Wadena south through Parkers Prairie into Douglas County. Minnesota Highway 78 extends south from Perham through the central part of the county to Battle Lake and continues south to Douglas County. Highway 108 heads west from Perham and connects with Interstate 94.
Three railway systems serve the county. One crosses the northeastern part of the county through Perham en route to the west coast; one crosses the southeastern part of the county and serves Fergus Falls; and the third crosses the central part of the county as it heads to the Canadian border. Grain elevators are located in cities and towns throughout the county.
Grain crops are marketed mainly in Fargo, North Dakota, and in Minneapolis, St. Paul, and Duluth, Minnesota. There is a sugar beet processing plant in Wahpeton, North Dakota. Livestock are marketed locally in the county at Fergus Falls and Perham, or they are marketed at West Fargo, North Dakota; Sisseton, South Dakota; or South St. Paul, Minnesota. A turkey processing plant is located at Pelican Rapids. A cheese processing plant and other food processing plants are in Perham.
There are six airports in the county. The Battle Lake, Henning, New York Mills, and Pelican Rapids airports have grassed runways. The airports in the cities of Fergus Falls and Perham have paved runways.