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Cow Island, Montana
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.
==The Missouri Breaks==
To understand the historical significance of Cow Island, one has to first know the basic facts about the Missouri Breaks. The Missouri Breaks are steeply eroded badlands along the east-west trending Missouri River. The breaks extend along the river from below Fort Benton down to Fort Peck, a distance of over 200 miles. The breaks also reach out for miles into the prairie from both the south and north bank of the Missouri River. The breaks are so difficult to access that this stretch of the Missouri River is still one of the most remote and untouched areas of Montana.
The breaks were formed during the last ice age, when a continental ice sheet extended down from Canada, and blocked off the previous drainage of the Missouri. The ice sheet backed water up into a large lake that filled a basin where Great Falls is now located. The rising lake waters finally broke out from the ice dam. As the lake waters rushed out, they carved a new river channel for the Missouri along the edge of the existing continental ice sheet. This sudden erosive action cut out the current channel of the river from below present Fort Benton, to the present Fort Peck Dam. This new channel was cut into soft Cretaceous age sedimentary rock, and tributaries then eroded down to the Missouri from each side. The tributaries were quickly carved by water erosion into the same soft Cretaceous age layers on both sides of the new river channel, thus creating the steeply eroded badlands known as the Missouri Breaks.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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