1. U.S. defense map and Western Hemisphere strategic bases army camps, forts, flying fields, air bases, naval bases, mileage distances and flying times between important points, Panama Canal defenses, U.S. Navy patrol areas, proposed patrol outposts in the Pacific, pan-American neutrality zone, main transcontinental highways, the Monroe Doctrine. [cartographic material] Yale Public content 1941. 2013-02-20T21:55:01Z. 2016-11-22T22:09:43Z. Rand McNally and Company. Richfield [Oil Corp. English. Public. United States and Western Hemisphere.