The 1803 Louisiana Purchase only accelerated the westward movement of Virginians out of their native state. Many of the Virginians whose grandparents had created the Virginia Establishment began to emigrate and settle westward. Famous Virginian-born Americans affected not only the destiny of the state of Virginia, but the rapidly developing American Old West. Virginians Meriwether Lewis and William Clark were influential in their famous 1804-1806 expedition to explore the Missouri River and possible connections to the Pacific Ocean. Notable names such as Stephen F. Austin, Edwin Waller, Haden Harrison Edwards, and Dr. John Shackelford were famous Texan pioneers from Virginia. Even eventual Civil War general Robert E. Lee distinguished himself as a military leader in Texas during the 1846–48 Mexican–American War.