47°46′20″N 108°56′52″W / 47.77222°N 108.94778°W Cow Island lies in a left turning bend of the Missouri River, in the area known as the Missouri River Breaks. The island is formed by sediments that are seasonally washed out from the mouths of Cow Creek and Bull Creek, which enter the Missouri River just upstream from Cow Island. The island is about 1.2 miles long and averages about 150 yards in width. It is located in extreme northern Fergus County, but lies across the river from extreme southern Blaine County, to its east.
Cow Island was significant in Montana's pre- and early history period as a Missouri River ford, and during the segment of Montana territorial history from about the mid-1860s to the mid-1880s, when it was used as a trans-shipment point for freight going upstream by steamboat to Fort Benton Montana. Cow Island's historic significance is related to its geographic location. Access to the Missouri River was difficult along a 200-mile stretch of river, because the Missouri breaks form a barrier to travel on each side of the river. However, a travel route known as the Cow Island Trail went north from Cow Island up Cow Creek, by-passing the breaks and emerging onto the Montana plains. This outlet through the Missouri Breaks caused Cow Island to be utilized as a historic Missouri River ford in the Missouri Breaks area. Starting in the 1860s this access route also caused Cow Island to become a steamboat landing site from which freight was moved up Cow Creek on the Cow Island Trail to Fort Benton and other destinations. During the Nez Perce War in 1877 the Nez Perce forded the Missouri at Cow Island, and it became the site of the Battle of Cow Island.
