The Corps of Discovery left its winter camp near the Mandan villages on April 7, 1805. By the 10th, according to their estimate, they had covered 45.5 miles, though it's actually about 65 miles from the presumed site of Fort Mandan to the vicinity of their encampment of this date.
Set out at an early hour this morning. At the distance of three miles passed some Minetares1 who had assembled themselves on the Lard shore to take a view of our little fleet. . . .
The country on both sides of the missouri from the tops of the river hills, is one continued lefel fertile plain as far as the eye can reach, in wich there not even a solitary tree or shrub to be seen except such as from their moist situations or the steep declivities of hills are sheltered from the ravages of the fire. . . .
At 1 P. M. we overtook three french hunters who had set out a few days before us with a view of traping beaver. They had taken 12 since they left Fort Mandan. These people avail themselves of the protection which our numbers will enable us to give them against the Assinniboins who sometimes hunt on the Missouri and intend ascending with us as far as the mouth of the Yellow stone river and continue there hunt up that river. This is the first essay of a beaver hunter of any discription on this river.
1. Hidatsa Indians. Minetare, or Minitare, meaning "water ford," was the Mandan Indians' name for the Hidatsa people. Some unidentifiable person, at some unknown point in time, for some unexplainable reason, evidently made a sign-language gesture indicating "hungry" in reference to this tribe. A French trader, interpreting the gesture to mean gros ventre, or "big belly." Lewis and Clark understood Minitare and Big Belly to refer to the same people.
Today, Indian ethnology makes a clear distinction between the two. The Gros Ventre are an Algonkian-speaking people who live with the Assiniboines on the Fort Belknap Reservation in northeastern Montana. The Hidatsas, sometimes referred to as the Gros Ventre of the Missouri, belong to the Siouan linguistic family.
See Eagle/Walking Turtle, Indian America: A Traveler's Companion (Fourth edition, Santa Fe: John Muir Pulibcations, 1995), 34-37.