San Martin was the only habitable planet in the Trevor's Star System, and home to the Republic of San Martin, an independent star nation that eventually became part of the Star Kingdom of Manticore. San Martin was a very dense world, with a gravity 2.7 times that of Earth. The planet was one of the heaviest-gravity worlds that man had ever settled. Its sea-level air pressure was high enough to produce near-toxic concentrations of carbon dioxide and nitrogen. This fact limited the population to mountain ranges, plateaus, and other high altitude locations. (HH2)