Marsh was a key figure in the intellectual ferment from which the conservation movement sprang in the mid-1800s.

He spent his childhood at the Marsh family's grand Federal house and adjacent farm in Woodstock, Vermont. The young man read and mastered languages and literature far beyond his years. He roamed the hills to learn about the natural world. Lawyer, congressman, diplomat, and man of wide ranging interests, Marsh helped to found the Smithsonian Institution and argued for the Union cause in Europe during the Civil War. He authored many books that broke new ground in the arts, sciences, languages, and history.

Marsh’s book Man and Nature, written while he was US Minister to Italy and published in 1864, is considered a founding text of the environmental movement.