This chapter presents a collection of first-generation Swiss geologists, who, around 1900, went abroad in order to work for oil organizations, both public and private. With the rise of oil exploration after 1900, the demand for experienced oil geologists grew rapidly. Oil companies started hiring trained geologists from different parts of the world, which led to an increasing number of Swiss geologists finding employment abroad. One of the first to start his career abroad was Carl Schmidt (1862–1923) from Basel, highly esteemed and later renowned for his achievements as a teacher of younger oil geologists. Another was Josef Erb (1874–1934), who accomplished an unparalleled career at Royal Dutch Shell. Other examples include Hans Hirschi (1876–1964), who worked for the Union des Pétroles d’Oklahoma for a few years, and Arnold Heim (1882–1965), working nearly 50 years for major oil companies. Many more followed over the decades to come, so that virtual successions took place between them: specific territories and specific companies were ‘handed down’ between geologists of the same nationality. Where once the Swiss were employed, others took over; the pioneers acted as door-openers for future generations.