BEYOND THIRTY (aka THE LOST CONTINENT) (Edgar Rice Burroughs Science Fiction/Fantasy Series #2)

The novel, set in the year 2137, was heavily influenced by the events of World War I. In the future world depicted in the novel, Europe has descended into barbarism while an isolationist Western Hemisphere remains sheltered from the destruction. The title Beyond Thirty refers to the degree of longitude that inhabitants of the Western Hemisphere are forbidden to pass. The title was changed years later to THE LOST CONTINENT.