The Missouri River played an important role in the history of Atchison County. Located about halfway between Atchison and Leavenworth was an island of more than 1,000 acres. Although it was never settled or planned as a town, this island has been the subject of many historic occurrences which deemed it as an “early settlement.” It was noted in the travels of Lewis and Clark in 1804 that it was the scene of important Indian councils and was once occupied by Col. Henry Leavenworth.
There are two explanations as to how this island got its name. One theory is that a lone cow was wandering about when French explorers came up the river. It’s entirely possible that a buffalo cow had strayed from the vast herds that roamed the region. Others believed that the cow had been stolen by the Indians from the settlement of St. Charles and placed on the island so it could not escape. The date of discovery is not known but when the Bourgmont expedition came through in 1724, the ruins of a trading post of French explorer Perrin du Lac were found.
The first military fort established in Kansas, named Cantonment Island, was set up on Cow Island. In 1826, Colonel Henry Leavenworth and his troops evacuated Fort Atkinson and came down river to make their winter quarters at Cow Island, which was by then called Camp Grogan. In the spring, floods came several times causing them to evacuate down river to establish Fort Leavenworth in the spring of 1827.
Although Cow Island was the site of various French posts and military forts, periodic floods swept away all remains of occupancy. A flood in 1881 threw the main channel to the Kansas side and left the island nothing more than a broad tract of bottom land adjoining the Missouri side. However, Cow Island is still Kansas soil though it is contiguous with the mainland of Missouri. There was a court case in 1900 by a man who was arrested for selling liquor in Missouri. His saloon was located on land that had been located on the island. They made the decision that the boundary would remain as it was before the sudden change of a flood, which was the middle of the navigable channel.
Some say that children living on this tract in later years had their tuition paid for by Atchison County but attended school in Missouri. Others say that on election days the men on this island tract of land were required to cast their votes in Kansas. It has been determined that this old settlement called Cow Island is under the jurisdiction of Platte County, Missouri. It seems that Atchison County has lost one of its most important historical spots, the forgotten Cow Island.