Thomas Jefferson, America’s third president, was more comfortable working the soil and tending his crops at Monticello than he was addressing Congress. In fact, in his whole life, Jefferson never traveled west of Harper’s Ferry in West Virginia. But he was not a simple man. Driven to uncover the truth behind every speculation, Jefferson was a persistent scientist, whose interests ranged from meteorology to biology and everything in-between, including mapmaking and the study of Indian languages.

He was a prolific writer, tackling subjects as weighty as foreign policy, public education and philosophy. At age 33 he drafted the Declaration of Independence, and as a member of Congress, he wrote a bill establishing religious freedom. But his favorite subject was the marvelous natural world around him.

Every day, Jefferson faithfully recorded the temperature and weather conditions and his observations on plants and animals. It’s no wonder that he required the same of Lewis and Clark throughout the expedition.

In a letter Lewis wrote to Clark before the expedition, Lewis described Jefferson as “the Main Spring of the action.”

It may have been Captains Lewis and Clark at the helm of the keelboat on May 14, 1804, but it was Jefferson’s enthusiasm that pushed them forward.