Point of Observation No. 51

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Lewis and Clark Celestial Observations at Fort Mandan

Point of Observation No. 51 (1804)
2 November 1804 through 17 April 1805

During the final weeks of October 1804, the Lewis and Clark Expedition awoke to temperatures near or below the freezing point. Blustery northern winds brought icy rain and snow. V-formations of honking geese filled the skies daily, winging their way south to escape the rigors of the northern winter. Meanwhile, contrary to the flow of the river and the advance of the cold, the Expedition pushed northward. On 27 October, after having traveled more than 1200 river miles from the mouth of Kansas River by their estimate, the Corps arrived at the Mandan-Minnitari villages near the mouth of Knife River (near present-day Stanton, North Dakota). William Clark spent part of the next few days seeking a suitable site for the Expedition's winter quarters. He chose a location a few miles downstream from the villages but on the east side of the Missouri. By 2 November 1804, with construction just getting underway,the captains named the encampment Fort Mandan in honor of their Mandan neighbors.

The Setting, Knife River

Reconstructed Fort Mandan

Fort Mandan from the air

© 2000 Jim Wark, Airphoto

A late winter snow squall has dusted the leafless cottonwood trees and the dormant grainfields. The triangular structure at photo center is a replica of Fort Mandan built by local volunteers in 1972. It is two miles via good roads from the Lewis and Clark Visitor Center at Washburn, North Dakota. The original site of the fort, where no remains have ever been found, was about fifteen miles up the Missouri from here, closer to the mouth of the Knife River. Access to it is discouraged.

The two ranks of cottonwood trees, which take root a short distance from water, mark the shifting of the river's course over a period of many years. Annually, those snow-covered sand bars are submerged by the spring freshet. When the high water recedes, they will have been moved and reshaped by the river's current. The Corps of Discovery often used the ice-covered river as a travel route, but the Missouri has not frozen solid in this vicinity within the past fifty years, mostly because the dams upstream—chiefly Garrison Dam, 35 miles away, and Fort Peck Dam 382 miles above that—have changed the temperature and velocity of the river's current.

—Joseph Mussulman and Robert Bergantino

A Chronology of Coordinates for the Mandan Villages and Fort Mandan
Date Source Coordinates
1797 Atlas Map 51 48˚N, 110˚W, approximately, villages
Evans ca. 1797 Atlas Map 12    “This meridian2 is 7˚23' west longitude from Ft. Charles or17˚33' west of St. Louis3 calculated from the parallel of the middle[?] latitude.”
Latitude by observation 47˚42'35" 4
Variation of the compass 1 point N.E.5
1798 Jan 10 Thompson, D 47˚17'22", 101˚14'24"6
1803, King Atlas Map 2 47˚25'N, 101˚05'W7
1805, Clark Atlas Map 32a 47˚31'N, 101˚08'W, Fort Mandan (State Department copy)
1805, Clark Atlas Map 32b 47˚32'N, 101˚02'W, Fort Mandan (War Department copy)
1805, Clark Atlas Map 32c 47˚33'N, 101˚02'W, Fort Mandan (Hague copy)
1805 Atlas Map 33 47˚21'47", no longitude recorded, Fort Mandan
1805 Atlas Map 46 47˚21'47", no longitude recorded, Fort Mandan
1806, L&C Atlas Map 123 47˚28'N, 100˚48"W, Fort Mandan
1810, Clark Atlas Map 125 47˚15'N, 100˚57"W, Fort Mandan
1814, L&C Atlas Map 126 47˚22'30"N, 100˚57'30"W, Fort Mandan
1997 May Bergantino8 47˚16'52"N, 101˚16'44"W Ft Mandan (1927 N. American Horizontal Datum)
  • 1. Maps numbers are those given in Moulton, Journals, Vol. 1.
  • 2. The meridian identified passes through the Mandan village.
  • 3. St. Louis is at about 90°10' west, thus the Evans map would place the Mandan village at about 107°43' W.
  • 4. This line is shown several miles south of the Mandan village.
  • 5. That is, 11¼° East.
  • 6. From Thompson's celestial observations.
  • 7. These coordinates for the Mandan village are approximate and likely are from David Thompson's celestial observations.
  • 8. The coordinates of this encampment were determined by "best-fit"-matching the Expedition's latitudes and river survey to a detailed map by G.K. Warren (1856), a map by the Missouri River Commission (1895), "modern" maps and aerial photographs and descriptions of the site by early travelers.