Harold Weston was born in Merion, Pennsylvania. He attended Harvard University, where he studied art and began to paint.  Polio contracted as a teenager made him unfit for military service during World War I, but he was attached to the British Army from 1916–19 as a YMCA volunteer and military artist in India and Mesopotamia (now Iraq).

Returning to the United States in 1920, Weston built a one–room studio in the Adirondacks at St. Huberts, NY, a site with which he would be associated for the rest of his life. His first exhibition of Adirondack landscapes at Montross Galleries in New York in 1922 was both critically and commercially successful. Due to illness, Weston was forced to leave the Adirondacks during the years 1926–30.  He and his young family went to Paris but settled in the Pyrenees.  He returned to New York City and then to St. Huberts in 1930.

From his studio in the Adirondacks in 1936-38, Weston painted murals for the General Services Administration Building in Washington DC.  During World War II, he was in Washington planning for provision of food to postwar Europe, having seen famine first hand in the Middle East during the First War.

An indefatigable organizer, Weston was active in artists and conservation groups and served as advisor to both national and state governments.  He was also an author, publishing Freedom in the Wilds the year before his death.