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Navigation for Lewis and Clark: Theodolite

Lewis & Clark National Historic Trail

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This photo is of one of Mr. Jefferson’s theodolites and is on display in his study at Monticello.

Photo: Thomas Jefferson Foundation

As they set off on their epic journey of many purposes, Captains Lewis and Clark took along a wide array of mathematical instruments to help them chart and survey the nation’s land acquisition. This set of sophisticated tools included a theodolite – used to measure vertical and horizontal angles.

There was much debate about bringing along a theodolite, as some felt such an instrument was too delicate for the long, arduous journey. Both Lewis and Thomas Jefferson, however, believed it was essential, and the president (who knew all about surveying) offered to lend his personal theodolite.

Mr. Jefferson’s theodolite was created by Jesse Ramsden, a famous British instrument maker, also known as the developer of the “Great Theodolite,” a massive instrument that could accurately measure over a distance of 70 miles.

Source: “The Scientific Instruments of the Lewis and Clark Expedition,” by Silvio A. Bedini, Smithsonian Institution



Lewis and Clark NHT Visitor Centers and Museums

This map shows a range of features associated with the Lewis and Clark National Historic Trail, which commemorates the 1803-1806 Lewis and Clark Expedition. The trail spans a large portion of the North American continent, from the Ohio River in Pittsburgh, Pennsylvania, to the mouth of the Columbia River in Oregon. The trail is comprised of the historic route of the Lewis and Clark Expedition, an auto tour route, high potential historic sites (shown in black), visitor centers (shown in orange), and pivotal places (shown in green). These features can be selected on the map to reveal additional information. Also shown is a base map displaying state boundaries, cities, rivers, and highways. The map conveys how a significant area of the North American continent was traversed by the Lewis and Clark Expedition and indicates the many places where visitors can learn about their journey and experience the landscape through which they traveled.

Last updated: December 30, 2019

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