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Dakota Datebook

A Miscalculation at Fort Mandan


To err is to be human. One of the most common human mistakes is estimating time. We say we’ll be there in 20 minutes, but it actually takes twice as long. These types of miscalculations have been going on for as long as people roamed the earth. One of the biggest miscalculations in recorded history happened here in North Dakota.

The Corps of Discovery first arrived in what is now North Dakota on October 14th, 1804. The men found the landscape beautiful, but worried as they felt winter on the wind. Sure enough, after five more days of travel it snowed. They knew they needed to take shelter for winter, so were quite relieved when they met the friendly Mandan and Hidatsa towards the end of October.

Happy with their situation, the Corps began building what became Fort Mandan about 12 miles  from the location of current-day Washburn. After almost two months of chopping and hoisting cottonwood trees, the men finally finished the fort on December 24th, just in time for Christmas. On Christmas Day, they flew the nation’s flag, marking the first time it had flown over North Dakota.

Their joy would soon be tempered by a harsh winter, with viscous winds and temperatures as low as -45. While the Mandan and Hidatsa understood the power of insulated earthen lodges, the explorers’ poorly insulated cabins forced them to burn large amounts of wood to stay warm. In the midst of the winter on this 7 degree, snowy date history, Clark decided to calculate how long it would take to get home. He was off by almost a year.

A lot of factors went into this miscalculation. For one, the expedition was in uncharted territory. While the Mandan and Hidatsa shared what travel information they could, they had always travelled west on horseback, not by boat, and they had never gone past the Rocky Mountains. That meant Clark was making little more than a guess when he estimated that that it would take three months to reach the ocean from the Rocky Mountains. He was also likely cold, and wishing to be optimistic.

The men left Fort Mandan in April 1805 in high spirits and continued to be awed by the beauty of the countryside throughout their journey. But it wasn't until November 15th that they finally reached the Pacific Ocean, and it would be an additional 10 months before their return to St. Louis.


Dakota Datebook written by Lucid Thomas









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