Lewis Linn was born near Louisville, Kentucky, on 5th November, 1796. After studying medicine he served in the 1812 War as a surgeon. In 1826 Linn worked as a doctor at Saint Genevieve, Missouri, where he had to deal with two cholera epidemics.

In 1836 Linn was elected to the United States Senate. Over the next few years Linn argued that the United States should absorb all of North America. Linn was particularly keen for the British to be pushed out of Oregon. In an attempt to persuade Americans to settle in Oregon he introduced a bill into the Senate granting free land as a reward for those prepared to travel across the Rocky Mountains to claim it. Other politicians argued that this legislation would result in a war with Britain and the bill was defeated.

Linn was chairman of the Committee on Private Land Claims and a member of the Committee on Agriculture.

Lewis Linn died in Saint Genevieve, Missouri, on 3rd October, 1843.