The Best Wood for World War I Airplanes | National Air and Space Museum https://airandspace.si.edu/air-and-space-quarterly/issue-14/world-war-one-lumber-divisions
To manufacture thousands of airplanes for its World War I allies, the Army formed the Spruce Production Division (SPD) to meet the demand.
What was needed most, though, was lumber—more than 100 million board-feet cut to
