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Decision at the Marias

By: Phil Scriver, LC200 Historian

As the Lewis and Clark Expedition labored up the Missouri from their winter camp at Fort Mandan, passing through the almost storybook White Cliffs area, they reached the mouth of the Marias River in early June. They had been told about other rivers that joined the Missouri from the north and from the south by the Indians they wintered had with, but this one was a completely unexpected surprise. This one was not on the maps Captain Clark had sketched during the long cold winter on the Dakota plains. This was the Expedition’s first major geographic decision. They must determine which river was the correct river to continue following. In opposition to every other member of the group, the Captains selected the more southerly flowing of the two as the one to lead them over the mountains. Their accurate determination of which river was actually the Missouri enabled the Expedition to press on with the journey to the Pacific without the costly retracing of steps that would have been caused by taking the wrong route. It has been said that the wrong decision here would certainly have spelled failure for the Corps of Discovery by forcing them to abandon all efforts to reach the ocean and head back down river. Captain Lewis reflected on this very possible problem in an early June entry in his journal.

How could the Captains so boldly select the river to follow in direct opposition to every other Expedition member? Although the Captains were well accustomed to making decisions this one was obviously not made quickly or without deliberate considerations. To get an idea how important this decision was, the Expedition spent eight days trying to determine which course to follow.

The Expedition had arrived at the mouth of the Marias the evening of June 2. The next day was spent trying to determine which river to follow. Sgt Pryor took two canoes and five men up the north fork about 10 miles while Sgt Gass took five men and two canoes up the south fork about 7 miles. Several small parties were sent out by land to try to determine where these rivers lead. All were to only go so far that they could return by nightfall. One of the overland parties was Joseph and Rueben Fields who followed the south fork about seven miles then turned north to the Teton and followed it back downstream to where it flowed into the Marias and then to the Missouri. The two Captains walked up to the high point of land between the two rivers but could not make any determinations so they busied themselves with measuring the rivers and trying to analyze the results.

Lewis noted that the north fork is very muddy and appears exactly like the river they had been following while the south fork was clear with a rocky bottom and much faster current. He deduced that the north fork gave color to the river downstream. For it to be so muddy it had to pass a great distance through the level plain. He suspicioned it did not enter the mountains to the west but drew its waters from the plains to the north. The south fork was precisely characteristic of a river that comes out of the mountains. These deductions were still not adequate evidence. So when the parties all returned that evening with no real success in determining which river to follow, the Captains determined they had to send a party up each one far enough to be certain the course to take. Lewis would lead a party up the north fork and Clark would take a party up the south fork.

On June 4 Lewis departed with Pryor, Drewyer, Shields, Windsor, LePage and Cruzatte up the east side of the Marias River to a high hill that afforded them a commanding view of the countryside. The party spend two days traveling up the river 77 miles. On the morning of June 6 Lewis is convinced that the north fork goes too much to the north to be the river to the great falls and determines to return to the mouth. To illustrate his decision, Lewis named the north fork the Maria’s River. They reached the main party’s camp the evening of June 8. As an interesting side note, not only had the party taken the latitude reading to determine where the were and studied the countryside to try to guess where the river they were following would lead, but they had time to identify two birds new to science; McCown’s longspur and the sage grouse.

At the same time Lewis departed up the north fork, Clark set out up the south fork with Rueben Fields, Joseph Fields, Gass, Shannon and York. They traveled 25 miles upriver to present day Carter that day. They next day it only took 11 more miles until Clark discovered “the river run west of south a long distance and has a strong and rapid current, going up further would be useless.” Clark had made his decision that the south fork was the river that would take them to the great falls. He started back to their main camp striking out overland to the Tansey River. They followed that river, reaching camp the following evening.

The Captains spent June 9 reviewing the results of their explorations. The old maps Lewis had brought with him, although they were being proven inaccurate in some details showed only small streams coming from the mountains to the north, the direction the Marias River went. Additionally the south fork was the same clear color the Mandans had told them the river at the falls was. Finally the formation of the several mountain ranges to the southwest was more reasonable for navigatible rivers to flow through than the single unbroken chain of mountains farther north. After studying all the information the two Captains were convinced that the south fork was the true Missouri. However the men were united in their belief that the north fork was the proper route, but “they said very cheerfully that they were ready to follow us anywhere we thought proper to direct.”

Finally a deal was struck. Lewis would take a party overland up the south fork until he reached the great falls while Clark would follow with the boats and rest of the party. When Lewis reached the falls he would send a message back down to Clark. After two days final preparations Captain Lewis set out on June 11. Accompanying Lewis were Joseph Fields, Drewyer, Goodrich and Gibson. Captain Clark departed with the rest of the Expedition and the boats the following day.

Although this area was of no special importance to the nomadic tribes who wandered the area in the days before Lewis and Clark, it has always been important for the white men starting with the Corps of Discovery. A look at the Montana map shows that bands of Indians may have followed the Missouri River across the eastern part of the state from the Yellowstone to the middle of the state, but the river makes a bend north just beyond the Judith River. Since they were riding horses and not bound to the river, they would probably have left the river at that point in favor of a shorter overland route to the rich hunting grounds at the great falls of the Missouri. Thus they would bypass the mouth of the Marias.

The area was extremely important to the Corps of Discovery. Similarly, it soon became very important to the fur traders that followed the Expedition.