The Lewis and Clark Expedition Map of the Rocky Mountains

How Master Cartographer William Clark Set Out to Map the Rockies

Route of the Lewis and Clark Expedition, 22 May 2014 | Victor van Werkhooven

It was 1803 when President Thomas Jefferson and his like-minded band of enlightened souls embarked on a shared journey to the far reaches of the American Republic … a journey that was as spiritual as it was geographical, as bold as it was foolhardy. At the direction of the President, Captain William Clark accepted the charge of Expedition Cartographer, and along with his partner Meriwether Lewis set out to set the contours of our nation with paper and ink, and with it the iconic shape of the Rocky Mountain West.

When people think about Lewis and Clark crossing the Rocky Mountains along with the other 45 members of the Expedition, they usually think of high-octane adventurers who are leaping through forests, climbing impossible rock faces, or battling the vicious grizzly or the occasional hostile natives. While not all of these images are inappropriate, they are by and large the result of romantic exaggeration … something that our species seems to excel at.  While there is no denying the heroic character of the Corps of Discovery, their chief members were scientists through and through, spending their days making careful calculations and following them up with carefully curated notes.

In our modern parlance: closer to nerds than jocks. Fortunately this is precisely what puts the Lewis & Clark Expedition near the top of the list of the most important scientific undertakings of our nation’s history, right up there with the moon landing.

Meriwether Lewis (1774-1809), co-leader of the Lewis and Clark Expedition, watercolor by Charles Balthazar Julien Fevret de Saint-Memin, 1807 | Everett Historical

Big Budget Item: Lewis & Clark’s Famous Chronometer

Packed tightly in the bags and parcels of the expedition members was a lot more than just beans, dried meat, and extra blankets. Cases up cases of scientific instruments were hauled from one side of this country to the other, up and over the Rocky Mountains and then back again. Of course, it was to be expected that many of these would break, so they had to bring more than a few backups.

In the end, the cost of the scientific gear became the most expensive part of the expedition.  The most famously pricey element was a gold-cased chronometer, which Lewis purchased from a Philadelphia watch mater before setting out on the journey. Also known as an “Arnold’s Watch”, this was a complicated piece of equipment at the time that was not manufactured in the United States.

As a simple time-keeping device, the chronometer allowed Lewis to make measurements of how much distance was being traversed per unit of time, which was why the resulting expedition maps were so astoundingly accurate for the time.

At $250, however, with an additional seventy five cents for the winding key, the Gold Chronometer accounted for nearly 10% of the expedition’s total budget. This is one case where we can all agree that it was worth the government’s cheddar.

Not Much to Go By: The Early Maps of the “Montagne de Roche”

1803 Lewis and Clark map, annotations in brown by Meriwether Lewis, tracing Mississippi and Missouri Rivers, Lakes Michigan, Superior, and Winnipeg, onwards to the Pacific. by Nicholas King, ca.1803 | Everett Historical
Click for larger image.

The Two Captains of the Corps of Discovery didn’t have much to start with when planning their journey across the Rockies. Their initial research was based off the work of one Nicholas King, who himself was working off the previous maps of Aaron Arrowsmith. (Don’t worry, there won’t be a test). This initial map assumed that the Rocky Mountains were a single line of comparatively straight mountains … and not likely much of an endeavor to cross.

Lewis & Clark, however, were already familiar with the concept of parallel mountain ranges, such as the ones that make up the massive mountain system that is known as the Rockies. Their doubts were solidified when the expedition received an updated map that was the work of John Evans in 1804. Evan’s map was far more realistic, and was based off of a Spanish Expedition through the Rockies that to place in 1795, nearly a decade earlier.

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In 1805, William Clark spent the winter at Fort Mandan compiling all of his notes, experiences, and measurements into a magnificent map that was to be sent back to the President along with a letter explaining its significance.

While accurate to an astounding degree, Clark’s Map, like those of Evans, Arrowsmith, and King before him, were abridged projections of a mountain system that was, as of yet, beyond our best comprehension.  

The true width, length, depth, and majesty of the Rocky Mountains therefore became the heart of a quest that continues into modernity, even if the geographical mysteries have given way to the spiritual ones, and the spatial to the subconscious.

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