[2] George grew up in Manhattan, New York with his sister Ruth and brothers James and Robert AKA Bob.
[citation needed] From 1934-37, Marshall worked as an economist for the consumer division of the National Recovery Administration under Franklin D. Roosevelt's New Deal.
In the late 1940s and early 1950s, he worked with Paul Robeson, Dashiell Hammett, and William L. Patterson on litigation protecting the rights of African-Americans and American communists.
Marshall was called before the House Committee on Un-American Activities, where he was cited for Contempt of Congress for refusing to turn over records from the National Federation.
He spent his childhood summers at Knollwood, his father's Great Camp on the shores of Lower Saranac Lake; with his brother Bob Marshall he climbed all 46 Adirondack High Peaks (mountains taller than 4,000 feet), an accomplishment that made him a founding "46er".