After World War II, he retired to his farm "Gaston Hall" near Orange, Virginia.
He also wrote Vain Shadow (1947), a romantic biography of the Spanish conquistador Francisco de Orellana.
In the introduction, Spence wrote: "Vast stretches of the Amazon River remain today exactly as they were four hundred years ago, when Orellana first saw them.
Within the past decade, a scientific expedition into the upper basin, bearing the most modern equipment known to civilized man, was forced by fierce savages and fiercer sicknesses, to flee the jungle.
Yet Orellana, without medicines, maps, or scientific data, without even knowing where he was, transiently mastered the river four hundred years ago, an incredible achievement in the light of modern knowledge."