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Thomas Jefferson, President of the United States and visionary “fountainhead” of the expansion and exploration of the western area once said, “Nature intended me for the tranquil pursuit of science, by rendering them my supreme delight”. Of all nature, the study of plants absorbed more of his time and efforts than any other aspects. (However, with his wide-ranging technical background and extensive library, Jefferson was well informed in the areas of meteorology, waterways and navigation, animals (including fossils) and the American Indians). Dr. Benjamin Smith Barton, professor of botany at the University of Pennsylvania, referred to that exceptional knowledge and said that “in the various departments of …botany and zoology, the information of this gentleman is equaled by that of few persons in the United States.” Dr. Barton wrote the first textbook of botany in the United States, Elements of Botany; or Outlines of the Natural History of Vegetables (Philadelphia, 1803). Lewis purchased a copy of this book to take on the expedition. Another book related to botany on Lewis’s purchase list was Miller’s edition of Lineas in two volumes by Johann Sebastian Mueller (1779-1789). Barton did lend Lewis a copy of The History of Louisiana by Le Page Du Pratz, which he carried to the Pacific and back – returning it four years later. This book, with signatures of both Lewis and Barton on the flyleaf, in now in the archives of the Library Company of Philadelphia.

At the age of twenty-three, Jefferson was recording botanical and phenological observations in his “Garden Book” ex. Apr. 6. a bluish colored, funnel formed flower (possibly bluebell, Mertensia virginica) in lowlands in bloom.

As the years passed, his knowledge of all plants expanded so that in his Notes on Virginia he listed 130 plants common to his state of Virginia. He divided these into four groups: medicinal, esculent, ornamental, and “useful for fabrication”. He included the scientific name as well as the vernacular. As a Latin scholar, Linnaeus’ method of binomial classification came easily to Jefferson, and he was one of the first in our country to recognize the value of this universal botanical classification. His interest in plants included recognition of the economic importance of their international interchange and the introduction of beneficial plants into the United States.

In his charge to Lewis and Clark, Jefferson included, “Observe the soil and the face of the country, its growth & vegetable productions; especially those not of the U.S.” (Coues Vol 1, xxxvii). These observations, according to Jefferson, were to “be taken with great pains & accuracy, to be entered distinctly, & intelligibly for others as well as yourself…several copies of these, as well as your other notes, should be made at leisure times & put into the care of the most trustworthy of your attendants” (Coues Vol 1, xxxii). To Jefferson observation and note-taking were keys without which “history becomes fable instead of fact”. It is this emphasis on scientific matters that distinguishes this expedition.

On February 23, 1801 Jefferson wrote to Meriwether Lewis, who was then a paymaster in General James Wilkinson’s Army of the West, that he needed a private secretary.
Lewis received that letter here in Pittsburgh where he had just arrived from D’Etroit. Lewis quickly replied on March 10 accepting the position and left for Washington at once. However the weather and a lame mount delayed his arrival until April 1, 1801.

Lewis' Background:
Lewis had another Pittsburgh connection, helping putdown an insurrection in 1794 – the Whiskey Rebellion - at age twenty. After this he enlisted in the regular army and served under General “Mad Anthony” Wayne in his Northwest campaign against the Indians and British. He served in Legionville, Baden, PA and there met Clark and their friendship formed.

Not quite 27 years old (1774-1809), Lewis had long displayed a talent for adventure in the woods and fields. Jefferson later wrote that “he had a talent for observation which had led him to an accurate knowledge of the plants and animals of his own country.”

Lewis grew up in an atmosphere of reverence and usage of plants. His Mother, Lucy Meriwether Lewis, was an herb doctor, prescribing simples (vegetable drugs) and tending the sick in their county. So he knew the local plants with medicinal values, a knowledge that served him well in the field. And Jefferson, himself, leaned toward the use of botanical treatments along with a distrust of doctors because of the loss of so many of his beloved family members who died while being treated by scientific medicine/doctors.

Voyage of Discovery Preparation:
In spite of Jefferson’s distrust of doctors, Lewis was sent to study with Dr. Benjamin Rush in Philadelphia and to assemble the “scientific” medical supplies for the trip.

While in Philadelphia Lewis was directed to call upon the eminent scientists that would provide him with “a greater familiarity with the technical language of the natural sciences, and a readiness in the astronomical observations necessary for the geography of his route.” These included: Andrew Ellicott, Robert Patterson, Dr. Benjamin Rush ( a signer of the Declaration of Independence), Dr. Benjamin Smith Barton, and Dr. Casper Wistar – all members of the American Philosophical Society, the acknowledged aristocracy of science in the United States.

Expedition supplies – including botanicals:
The War Department directed Israel Whelan, Philadelphia, to assist Lewis in amassing the needed supplies and allocated $1,000 for the Expedition. Some 200 articles were purchased including193 pounds of portable soup, three corn mills, 130 rolls of pigtail tobacco, 30 gallons of “Strong Spt. Wine” along with presents for the Indians, 52 canisters for powder, medical and surgical supplies, mosquito netting and oil-skin bags. He took spices, salt, and the portable soup. Few comestibles were taken to save weight – with plans to live off the land. No special supplies for preserving botanical specimens (such as special papers) seem to be noted; however there was ink powder, metal pens, paper and sealing wax along with journals.

The total weight was estimated at 2,300 pounds and proved to be a considerable problem in getting the loaded wagons to Pittsburgh. These supplies seemed to be adequate as far as the estimated needs were made, based on 10-12 men. However the expedition numbers increased to 45, so other supplies were added at Forts Massac and Kaskaskia and at St. Louis. Trying to estimate all the needs of food, arms, clothing, camping equipment, scientific instruments, and presents for the American Indians presented a formidable task, especially since the extent of the expedition was not determinate. There were some mistakes in supply choices - the three Fahrenheit thermometers were all broken before the Rockies were crossed.

Preparation at Monticello had provided access to Jefferson’s library where Lewis could study Mark Catesby’s and John Bartram’s travel to the Carolinas, Georgia, and Florida; John Clayton’s Flora Virginica; an account of a journey to the Pacific by Alexander Mackenzie; and Linnaeus’ taxonomic volumes.

Note: The PRCST website has as a focus the scientific aspects of the expedition, with specific emphasis on the Pittsburgh and Pennsylvania contributions. In fact, the value of the entire Eastern Legacy is not often addressed in other websites. Since detailed descriptions and specimens of plant materials did not formally begin until the journey up the Mississippi R., this section on plants of the expedition will include information gained until the expedition camped at Fort Mandan.

The Pittsburgh Months:
Arriving in Pittsburgh and the confluence of the Monongahela and Allegheny Rivers on July 5, 1803 Lewis found that construction of the keelboat he had ordered had barely begun. Apparently the workmen imbibed too much of a product of the local rye crop – Monongahela rye. Inability to move the construction ahead proved to be a great frustration to Lewis. Perhaps this was one impetus for purchasing the Newfoundland dog, Seaman, during that time. The keelboat was not finished until the end of August.

Pittsburgh's rivers were significantly smaller in Lewis and Clark's day.  Water in the Ohio was at a record low at the time of their launch and slowed the initial pace of the expedition. On the trip to the Mississippi River conjunction signs of fall showed in touches of color in the leaves of the gum, buckeye and sassafras trees. Farmers were topping their corn and collecting their fodder. A heavy mast crop (except for the ‘beach”) on both sides of the river was noticed and squirrels were noted swimming the river. Walnut and hickory nuts seemed to be in abundance. Seaman jumped in the river and caught some of the squirrels.

Last minute supplies were bought before going up the Missouri: five barrels of pork, five barrels of flour, 25 ½ bushels of lyed corn (hominy) and several gallons of Woodsfords whiskey. Large quantities of corn were parched to be converted into meal. They melted 50 pounds of hog’s lard and 200 pounds of tallow that was stored in whiskey kegs after cooling. All of this – pork, lard, beans, dried apples, coffee, and sugar were packaged and stored in different places on the boat.

Lewis collected and sent to Jefferson two boxes of specimens – one in March and one in May 2004. Slips of “the great Osages Plums [Prunus sp.] and Apples [Osage orange, Maclura aurantiaca] were included. This was the first shipment of natural history specimens from west of the Mississippi. A letter from Lewis contributed “a short description of the Osage orange. The slips (cuttings), he said, came from trees owned by Pierre Chouteau, who had introduced them from an Osage Indian village 300 miles to the west. The tree itself was much like that of the common black haw, though less branched, and growing to a larger size, as much as 30 feet. Thorns covered the smaller branches. The fruit, of an “exquisite odour” when mature, was “the size of the largest orange, of a globular form, and a fine orange colour….So much do the savages esteem the wood of this tree for the purpose of making their bows, that they travel many hundred miles in quest of it.” This apparently was Lewis’s initial description of a plant then new to science.

During the weeks traveling upstream to the Kansas River, little note was taken of the lush riverbank vegetation, with references mostly to familiar trees such as oak, ash (used for oars), walnut, sycamore and cottonwood. As they went further west a decrease in vegetation was recorded. Near the entrance of the Osage River Lewis went ashore and collected many curious plants and shrubs (the original document is preserved by the American Philosophical Society). Lewis listed some plants with reputed medicinal qualities such as the yellowroot (Hydrastis Canadensis) and a species of wild ginger (Asarum). He also noted the narrow-leaved willow (Salix longifolia). He collected a packet of cottonwood seed near La Charette and recorded, “this specimine is the seed of the Cottonwood, which is so abundant in this country … this tree arrives at a great size, grows extremely quick the wood is of a white colour, soft spungey and light, pirogues are most usually made of these trees, the wood is not durable nor do I know any other purpose which it can answer except that just mentioned.” Lewis later revised his opinion of the Cottonwood (Populus deltoids occidentalis). Unfortunately the specimens collected below the entrance of the Kansas have not survived.

Note:  This tree grows rampantly in the Pittsburgh area.

Traveling north after the entrance of the Kansas R., near what is now Leavenworth, Clark described the surroundings – “The plains of this countrey are covered with a Leek green grass. Grass …Groups of Shrubs covered with the most delicious froot is to be seen in every derection, and nature appears to have exerted herself to butify the senery by the variety of flours …which strikes & profumes the Sensation”. The Leek green Grass he described may have been the big bluestem Andropogon sp.

On Wednesday, July 4,1804 Joseph Field was bitten by a snake – apparently not a venomous one. In those times the remedy for snakebite usually involved the use of some plants to be included in the poultices i.e. onions, radishes, and freshly chewed tobacco. Lewis used a poultice of bark and gunpowder. The use of gunpowder seemed to be more of a frontiersman ingredient rather than a medical prescription. The bark Lewis used could have been the inner bark of the slippery elm tree (Ulmus fulva). The inner part was mucilaginous and used often in poultices. He had, however, 15 pounds of pulverized Peruvian bark (Cinchona) and this was mentioned later in the use of other poultices.

Summer grapes and other wild fruits were added to their meals as they went upriver to the Platte R.. On July 19th, near the present-day Nebraska City, they gathered “ a quantity of cherries at noon and put them in the Whiskey barrel” and these were called by some “choak-cherries”. Floyd’s diary noted that “thos cherries they Gro on Low Bushes about as High as a mans hed”. Today botanists believe that the plants were the sand cherry (Prunus pumila).

The Plains Indians Lewis & Clark first encountered in this part of the journey occupied an area extending from southern Canada to the Rio Grande, a great expanse of grassland occupied by about 30 different tribes. They were nomadic tribes and grew no crops, depending upon other tribes for plant foods.

Plants collected that were new to science included:

  • OSAGE ORANGE. Maclura aurantiaca Nuttall= Toxylon pomiferum Rafinesque (Thwaites, VII, 295-297). Described by Rafinesque in 1817. Cuttings of this plant were sent by Lewis to Jefferson prior to the start of the Expedition.
  • RABBIT BUSH.. Bigelowia douglasii Gray = Chrysothamnus viscidiflorous (Hook.) Nuttall. 1840
  • PINK CLEOME. Cleome serrulata Pursh. 1814
  • BROAD-LEAVED GUM PLANT. Grindelia Squarrosa (Pursh) Dunal. 1814.
  • LARGE-FLOWERED CLAMMY-WEED. Polanisia trachysperma T.& G. 1840.
  • BUFFALOBERRY. Shepherdia argentea Nuttall = Hippophae argentea Pursh. 1814.

From this part of the journey the Lewis & Clark Herbarium includes:

  • HEART-LEAVED UMBRELLAWORT. Allinia ovata Pursh = A. nyctaginea Michx. Collected Sept.1
  • CANADA ANEMONE Anemone pennsylvanica L.= A.canadense L. August 17.
  • PASTURE SAGEBRUSH. Artemisia frigida Willdenow. Sept. 2.
  • RABBIT BRUSH. Bigelowia douglasii Gray. Sept. 2.
  • PINK CLEOME. Cleome serrulata Pursh. August 25.
  • FIELD HORSETAIL. Equisetum arvense L. August 10.
  • WOOD HORSETAIL. Equisetum sylvaticum L. August 10.
  • BROAD-LEAVED GUM-PLANT. Grindelia squsarrousa (Pursh) Dunal.August 17.
  • VIOLET PRAIRIE-CLOVER. Petalostemon violaceum Michx.= Petalostemum purpureum (Vent.) Rydberg. Sept.2.
  • LARGE-FLOWERED CLAMMY-WEED. Polanisia trachysperma T.&G. August 25.
  • BUFFALOBERRY. Shepherdia argentea Nuttall. Sept. 4. 

Further West:
Reaching the high plains just west of the 98th meridian, Lewis & Clark found fewer and fewer plants. (The high plains is one of three regions comprising the Great Plains and one of the largest grasslands in the world.) Instead there was a level treeless surface that ranged from a subhumid to an arid climate and a land of high winds and clear blue skies. Cutright records that “Henry Marie Brackenridge, a Pittsburgh lawyer and explorer who ascended the Missouri in 1811, reasoned that these features might be due to the openness of the country, which allowed the winds to chase away the haze, or to the ‘light dress of vegetation, with which these plains are clothed’, for ‘where the vegetation is luxuriant, dense vapors arise during the night; ad the noxious gases are produced, which floating into the atmosphere lessen the brightness as well as its purity.’”

Today, here in the Three Rivers area, we enjoy some of the same species of plants encountered by Lewis & Clark. Time and the increased impact of civilization moving westward through this “Gateway to the West” have left their marks. Alien species have been introduced including some invasive plants that crowd out our native species. Along with the changes in the Allegheny watershed, disease and pests have altered the extant flora. 

A study by the Center for Creative Inquiry, Carnegie Mellon University, inventoried the riparian areas of the Three Rivers. Data so far shows that 50% of the plants are still native species.

Other Links:

The Botany of the Lewis and Clark Expedition (University of Cincinnati)
Lewis and Clark as Naturalists (Smithsonian National Museum of Natural History)
Lewis and Clark Herbarium (University of Maryland and The Academy of Natural Sciences in Philadelphia in cooperation with Cornell University)
Botanical Art Stemming From the Lewis and Clark Expedition (1803-1806) - Frederick Pursh


Specimens of plant materials collected by Lewis and Clark were pressed for preservation and are held by the National Academy of Natural Sciences in Philadelphia.  The Academy's Lewis and Clark Herbarium houses 226 sheets of plants.

"Objects Worthy of Notice: Microscopical Anatomy of Selected Plants Collected by the Lewis and Clark Expedition" (A spectroscopic study of the floral preservation of some of these specimens and a research effort to ascertain the condition of the specimens.)

Material in this section is based on the information from:

  • Lewis and Clark: Pioneering Naturalists, Paul Russell Cutright, 1989, University of Nebraska Press.
  • Meriwether Lewis and William Clark: The History of the Lewis and Clark Expedition, Edited by Elliott Coues, Vol. I, Dover Publications – unabridged publication of the four-volume edition published by Francis P. Harper in 1893.
  • Lewis and Clark’s Green World: The Expedition and Its Plants, A. Scott Earle and James L. Reveal, 2004 Farcountry Press.
  • Lewis & Clark: Pioneering Naturalists, Paul Russell Cutright, 1969, University of Illinois Press
  • An American Epic of Discovery: The Lewis and Clark Journals – The Abridgement of the definitive Nebraska Edition. Edited and with an introduction by Gary E. Moulton 2003 Board of Regents – University of Nebraska


Animals encountered on the expedition were documented by drawings and descriptions. And, in a few cases, by collection and sending specimens to President Jefferson (ex. Prarie Dog).

The Natural History of the Lewis and Clark Corps of Discovery (Carnegie Museum of Natural History)

Lewis and Clark as Naturalists (Smithsonian National Museum of Natural History)


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