The White Mountains, by John Christopher, was published in 1967 by Simon & Schuster.
Long ago, the Tripods–huge, three-legged machines–descended upon Earth and took control. Now people unquestioningly accept the Tripods’ power. They have no control over their thoughts or their lives. But for a brief time in each person’s life–in childhood–he is not a slave. For Will, his time of freedom is about to end–unless he can escape to the White Mountains, where the possibility of freedom still exists.