Hidatsa Indians had captured the Shoshone girl Sacagawea some four years before she met Lewis and Clark. Around 1804 the Hidatsa sold her and another Shoshone girl to French trapper Toussaint Charbonneau, who married both.
In November 1804, at a Mandan village, Lewis and Clark invited Charbonneau to join their expedition and bring one of his wives. Charbonneau chose Sacagawea, then about 15 years old and 6 months pregnant.
Photograph by John Livzey