1742-43 Francois Louis Verendrye and companions are first white men to sight the Big Horn Mountains in Wyoming.

1803 Louisiana Purchase (including present Wyoming) is completed.

1805 General James Wilkinson is appointed governor of the region including Wyoming. Lewis and Clark employ Sacajawea as guide.

1806  John Colter explores Rocky Mountains (credited with being first native-born American to enter what is now Wyoming). Nicknamed area “Colter's Hell.”

1807 Ezekiel Williams heads trapping party into Wyoming. John Colter is first white man to enter Tog-Wo-Tee. Togwotee (pronounced Toe-gah-tee) Pass is not only one of the most mispronounced and misspelled locales in Wyoming, it is also a sight not to be missed in winter. The pass gets its name from Sheepeater Indian guide Tog-we-tee, a sub-chief under Washakie. Tog-we-tee means lance thrower or “exactly there” from an Indian game in which players threw lances to see how close they could come to the first one thrown. The winter of 2000/01 marked the 80-year anniversary of the official opening of a road over the pass in 1921.

1809  Many trappers operate in what now is eastern Wyoming.

1811  Wilson Price Hunt's party, employed by John Jacob Astor, crosses Wyoming; was the first organized expedition through Wyoming, on its way to Oregon (present-day Astoria).

1812  Robert Stuart and companions returning from Astoria cross the Continental Divide and discover South Pass; build first-known cabin in Wyoming on  the North Platte River near Bessemer Bend.

1822 General William H. Ashley establishes trading post on the Yellowstone River. Jim Bridger arrives with Gen. Ashley.

1824  Ashley party names Sweetwater River. South Pass is crossed by Ashley trappers, headed by Thomas Fitzpatrick and Jedediah Smith.