The Lewis and Clark Expedition (Corps of Discovery) was commissioned by President Thomas Jefferson following the Louisiana Purchase in 1803. While the primary goals were finding a water route to the Pacific and establishing American presence, a secondary objective was scientific documentation. Jefferson instructed the explorers to record information on the geography, climate, mineral locations, and the region’s flora and fauna.
Meriwether Lewis, the expedition’s commander, prepared for this task by studying botany, zoology, and medicine with scientists in Philadelphia. Though not a professional botanist, Lewis was tasked with meticulously cataloging the new plant species encountered. His personal interest in natural history aided him in identifying plants of medicinal or economic value.
The Corps employed a systematic, though rudimentary, methodology for collecting specimens. Lewis used a hand press to dry and flatten plant samples, which were then labeled with notes on their habitat, growth, and uses by Native American tribes. The explorers focused on collecting samples that demonstrated all the plant’s distinct features, including flowers, leaves, and fruit or seed pods. This careful preservation introduced the biological richness of the new territory to Western science.
Plants New to Science
The Corps of Discovery collected hundreds of plant specimens, including an estimated 178 to 202 species previously unrecorded by Western science. These discoveries spanned from flowering herbs and shrubs to towering conifers, providing the first comprehensive look at the diverse plant life of the American West.
One of the most notable finds was the Bitterroot, Lewisia rediviva, found in western Montana. Lewis first encountered and tasted the root, noting its use as an important food source by the Shoshone and Nez Perce tribes. The plant later earned its species name, rediviva, meaning “revived from a dry state,” because a specimen collected by Lewis sprouted after being deprived of water and soil for years.
Among the significant timber species documented were the Ponderosa Pine and the Douglas Fir. Lewis noted the Ponderosa Pine in May 1805, distinguishing it from eastern pines by its noticeably longer needles. This tree was later used by the expedition to construct five canoes. The journals also recorded species such as the Golden Currant, Ribes aureum, and the Western Snowberry, Symphoricarpos albus, which were unknown to scientists at the time.
The expedition also collected specimens of flowering plants like the Red False Mallow, Sphaeralcea coccinea, and various species of phlox. These collections provided evidence of the unique ecological zones across the continent, from the Great Plains to the high mountain ranges. Lewis meticulously recorded the common names used by the Native Americans, which provided context on the plants’ practical applications.
Specimen Preservation and Scientific Legacy
The survival of the Lewis and Clark botanical collection faced significant challenges due to the harsh conditions of the journey and the subsequent delays in cataloging. In 1805, the expedition sent a shipment of specimens and seeds back to President Jefferson from Fort Mandan, which included about 60 plant samples. The bulk of the collection returned with the Corps in 1806, totaling over 200 specimens.
Upon their return, Lewis entrusted the entire collection to Benjamin Smith Barton, a prominent Philadelphia physician and naturalist. Barton, in turn, hired the German botanist Frederick Traugott Pursh to organize, describe, and illustrate the plant specimens. Pursh spent years analyzing the collection.
Pursh formally introduced the discoveries to the world in his 1814 publication, Flora Americae Septentrionalis, or A Systematic Arrangement and Description of The Plants of North America. This work contained the first scientific descriptions of many Lewis and Clark plants, with Pursh naming several genera and species in honor of the explorers. For instance, the genus Lewisia was created for the Bitterroot, and Clarkia was named after William Clark. The expedition’s herbarium provided an unprecedented biological survey of the continent and remains a foundational collection in American botany, with many specimens now housed at the Academy of Natural Sciences in Philadelphia.