ventures At 19, Ludwig established a freighter business by transporting molasses and lumber around the Great Lakes. There are rumors of his engaging in rum running during the Prohibition era. In the 1930s, he developed a novel approach to financing further expansion, by borrowing the construction cost of tankers and using pre-agreed charters as collateral. His National Bulk Carriers became one of the largest American shipping companies, and he eventually owned about 60 vessels. In the 1940s, one of his shipyards in Virginia developed a method to use welding instead of riveting, which saved time during World War II, when there was huge demand for new ships. After the war, he had ships built in Japan, where labor costs were lower. His ships transported oil around the world; in the 1950s he pioneered the construction and use of the new oil supertankers. Ludwig diversified into a wide range of holdings: an oil refinery, banking, cattle ranching, insurance, and real estate. He invested in various mining and exploration projects on nearly every continent: the Americas, Africa, Australia and the Middle East. He created a chain of luxury hotels in Mexico, Bermuda and the Bahamas, and developed Westlake Village, California. At his peak, he owned more than 200 companies in 50 countries, and his fortune was estimated at $4.5 billion. Princess International Hotels Ludwig built or bought an impressive collection of hotels. These were: the Hamilton Princess and Southampton Princess in Bermuda; the Bahamas Princess (formerly the King's Inn) and the Xanadu Princess Tower (formerly the International) in Freeport; the Acapulco Princess and the Pierre Marques in Mexico; and the Francis Drake in San Francisco. The American millionaire recluse Howard Hughes acquired the Xanadu Princess in 1973, and lived there for the last two years of his life. Exportadora de Sal, SA In 1954, on a trip to Baja California Sur, Ludwig founded Exportadora de Sal S.A., which became the "Largest Salt Company in the World", at the Guerrero Negro lagoon. As the rural area was largely uninhabited, Ludwig arranged for the necessary workers and materials to be transported there to build a large, new town in the municipality of Mulegé. Here, the saltworks were established by pumping the brine to the surface and allowing it to dry. In 1973, with rumors that the Mexican Government would nationalize the company, Ludwig sold his interest in Exportadora de Sal, SA to Mitsubishi. It