 His family took him to the Adirondack Mountains when he was six months old; they returned every summer for the next 25 years.After that, Marshall returned often on his own.His younger brother George (1904–2000) later described the family's visits to Knollwood, their summer camp on Lower Saranac Lake in the Adirondack State Park, as a time when they "entered a world of freedom and informality, of living plants and spaces, of fresh greens and exhilarating blues, of giant, slender pines and delicate pink twinflowers, of deer and mosquitoes, of fishing and guide boats and tramps through the woods".