Little is known of the history of Cameroon before the 15th century, when the Portuguese arrived and established a slave trade on the coast. For the next 300 years Spanish, British, French, and German, as well as Portuguese, traders operated along the coast, chiefly to obtain slaves. The slave trade ended in the 19th century and commerce in palm oil and ivory became important. In 1884 Germany took control of the region and formed the colony of Kamerun. The Germans built cities, roads, and railways.

After Germany's defeat in World War I, the colony was divided by the League of Nations into two mandates, the British Cameroons and French Cameroun. Both mandates became trust territories of the United Nations in 1946. In 1948 the Union of Cameroonian People (UPC) was organized by French Cameroonians to work for unification and independence. The UPC launched a revolt in 1955, but it was quickly subdued by the French. In 1957 the UPC began a guerrilla campaign to end French rule.

In 1959 France granted Cameroun internal self-government and in the following year granted independence. Ahmadou Ahidjo was elected the country's first president. In 1961 the southern part of the British Cameroons joined Cameroun, forming a federated republic; the northern part joined Nigeria.

Ahidjo imposed an autocratic rule. His only opposition was the UPC, which continued to oppose central authority even after independence. In 1971 the UPC insurgency was crushed by the government.

Ahidjo worked to integrate the former French and British divisions of the country into one political and economic system. In 1972 he imposed a new constitution. Under his rule the country developed a large petroleum industry. Its revenues were used to improve agricultural production, making Cameroon self-sufficient in food. In 1982 Ahidjo resigned as president and was succeeded by Paul Biya. Mt. Cameroon erupted in 1999, producing a wall of lava 100 feet (30 meters) thick that cut off a major road link with Nigeria.