Reliable historical information about Sacagawea is very limited. She has become an important part of the Lewis and Clark mythology in the American public imagination. The National American Woman Suffrage Association of the early twentieth century adopted her as a symbol of women's worth and independence, erecting several statues and plaques in her memory, and doing much to spread the story of her accomplishments.

In 2000, the United States Mint issued the Sacagawea dollar coin in her honor, depicting Sacagawea and her son, Jean Baptiste Charbonneau. The face on the coin was modeled on a modern Shoshone-Bannock woman named Randy'L He-dow Teton. No contemporary image of Sacagawea exists.

Sacagawea was born into an Agaidika (Salmon Eater) tribe of Lemhi Shoshone between Kenney Creek and Agency Creek about twenty minutes away from present-day Salmon in Lemhi County, Idaho. In 1800, when she was about twelve, she and several other girls were kidnapped by a group of Hidatsa (also known as Minnetarees) in a battle that resulted in death among the Shoshone of four men, four women and several boys. She was taken as a captive to a Hidatsa village near present-day Washburn, North Dakota.

At about thirteen years of age, Sacagawea was taken as a wife by Toussaint Charbonneau, a Quebecer trapper living in the village. He had also taken another young Shoshone named Otter Woman as a wife. Charbonneau was reported to have purchased both wives from the Hidatsa, or won Sacagawea while gambling (the gambling is the more reliable of reports).[citation needed]

Sacagawea was pregnant with her first child when the Corps of Discovery arrived near the Hidatsa villages to spend the winter of 1804-1805. Captains Meriwether Lewis and William Clark built Fort Mandan. They interviewed several trappers who might be able to interpret or guide the expedition up the Missouri River in the springtime. They agreed to hire Charbonneau as an interpreter when they discovered his wife spoke Shoshone, as they knew they would need the help of Shoshone tribes at the headwaters of the Missouri.

Lewis recorded in his journal on November 4, 1804:

Charbonneau and Sacagawea moved into the expedition's fort a week later. Lewis recorded the birth of Jean Baptiste Charbonneau on February 11, 1805, noting that another of the party's interpreters administered crushed rattlesnake rattles to speed the delivery. Clark and other European Americans nicknamed the boy "Little Pomp" or "Pompy".

In April, the expedition left Fort Mandan and headed up the Missouri River in pirogues. They had to be poled against the current and sometimes pulled from the riverbanks. On May 14, 1805, Sacagawea rescued items that had fallen out of a capsized boat, including the journals and records of Lewis and Clark. The corps commanders, who praised her quick action, named the Sacagawea River in her honor on May 20.

By August 1805, the corps had located a Shoshone tribe and was attempting to trade for horses to cross the Rocky Mountains. They used Sacagawea to interpret and discovered that the tribe's chief was her brother Cameahwait.

Lewis recorded their reunion in his journal: