It is not known how long the people have inhabited the area. The first clear written references to Nyamwezi occur in the early nineteenth century. According to local traditions, most of the region was uninhabited until the seventeenth century, when chiefly families began to arrive from various directions. Some are said to have come as hunters. As the population grew, new chiefdoms were formed by expansion and division. Trading visits to the coast and other areas were common in the nineteenth century, and Indian and Arab traders visited the area from the coast. Tabora was established as an Arab settlement, probably in the 1840s. John Hanning Speke and Richard Francis Burton were the first European visitors, in 1857. During the next thirty years, foreign traders, explorers, and missionaries made frequent visits, and local traders continued to travel to the coast. Exports included ivory and slaves, and imports included cloth and, later, guns. Secular aspects of chieftainship seem to have developed strongly at this time, and Arab intervention in local politics brought them into conflict with a rising chief, Mirambo, whom Henry Morton Stanley described as the Napoleon of Central Africa. Mirambo established his influence over many other chiefdoms in the Nyamwezi and southern Sukuma areas, but this "empire" broke up shortly after his death in 1884. The colony of German East Africa was established in 1890, and the area was brought under control by 1893. The Germans ruled through local chiefs who were expected to keep order and collect taxes. Several chiefdoms that had formerly had matrilineal succession to the chieftainship changed to patrilineal succession under German rule. The British formally took over the administration of the country in 1919, three years after the expulsion of the Germans from Tabora during World War I. British rule continued until Tanzanian independence in 1961. Several changes were made in the number and internal organization of the chiefdoms in this period, and communications were extended and improved. Many people were moved from areas where sleeping sickness was prevalent into new settlements. Cotton was developed as a cash crop in Sukumaland. Since independence, chieftainship, as a political office, has been abolished, and the development of collective forms of village organization has been encouraged, albeit without much success.