In modern academic career systems there are a large number of entry positions, much smaller numbers of intermediate positions, and still fewer full professorships. We examine how this system has developed in Germany, the country where the modern academic system was introduced, tracing the historical development of academic positions since the early 19th century. We show both a differentiation and professionalization. At first, professorships and private lecturer positions were the only formal positions, but later, lower formal academic positions emerged. Over (...) the whole period, the share of higher academic positions steadily decreased. This differentiation process was closely connected to professionalization: remuneration through salaries was extended from professors to almost everyone working in the German academic system. We propose that the process of differentiation and professionalization was induced by the expansion and democratization of higher education. Finally, our study shows that the opportunities for PhDs to obtain salaried doctoral positions have increased since the 1950s. On the other hand, opportunities for PhDs to become a professor or obtain another tenured job have decreased since the 1980s due to a slowdown of higher education expansion. (shrink)