Each of the four British colonies must necessarily be treated as an independent unit, as each was so treated in British policy. The Gambia was merely a strip of land, averaging only seven miles in width, on either side of 292 miles of navigable waterway penetrating into what otherwise was French Senegal. Even in the 1950s its population did not exceed 300,000, and the possibilities for any sort of development were limited. In fact the colony achieved a fair degree of prosperity by concentrating on the production of peanuts, grown in part by farmers who migrated annually from Senegal for the purpose. By 1956–57 foreign trade was some $60 per capita and government revenue $14.

The Sierra Leone situation was one of a relatively dense population exploiting or even overexploiting a poor environment for its subsistence, and initially the most that was achieved was to develop some palm produce for export. During the 1930s the situation began to change when European companies began to exploit extensive diamond-bearing gravels and to mine high-grade iron ore. By the mid-1950s foreign trade, which had been $14 million ($9 per capita) in 1913–14, had risen to $101 million ($44). About half of this was based on the activities of the foreign-owned mining companies. These provided little local employment; and furthermore, large numbers of people had been led to abandon farming to dig for diamonds on their own account. This gave rise to numerous social, economic, and political problems, because legally the diamond-bearing grounds had been conceded to the European companies. These factors may explain why the increase in government revenue, and hence the capacity of the government to sponsor further development, was low in comparison with other western African territories. It rose from $3.6 million ($2.40 per capita) in 1913–14 to $27 million ($11.70) in 1956–57, a factor of increase of 4.9, which compares unfavourably with a factor of 21.1 for French West Africa as a whole, 11.4 for the Gold Coast, 6.1 for Nigeria, or even 5.9 for the Gambia.

The Gold Coast was a complete contrast, indeed one of the most successful examples of colonial development anywhere in British tropical Africa. The people of its coastlands were long accustomed to world trade, and indeed to British rule, with the result that the Gold Coast entered the colonial period with a very high level of economic activity. In 1912–13 its foreign trade was worth $42.5 million ($28.30 per capita) while government revenue was $6.5 million ($4.30 per capita). Subsequent development was facilitated by the possession, within a manageable area that was adequately but not too densely populated, of a considerable variety of resources.

The first railway was built inland from Sekondi in the southeastern Gold Coast between 1898 and 1903 with the dual purpose of supporting gold mining and ensuring political control of Asante. This railway subsequently was used for the removal of manganese ore and bauxite. Extensive diamond diggings, worked equally by individual Africans and by European companies, began to be developed from 1919 onward. But the mainstay of the economy became cocoa, which local farmers began to produce on small plots in the forest toward the end of the 19th century. They found a reliable market for their produce. Cocoa became the most valuable export when it outranked gold in 1913, and thereafter went on to contribute more than four-fifths of exports and to constitute something between a third and a half of the world’s supply.

The prosperity derived from cocoa in the 1920s enabled the governor, Sir Frederick Gordon Guggisberg, to pledge the country’s revenues for loans to finance a coherent program of economic and social development. The Gold Coast’s first deep-water port was built at Takoradi, the cocoa-producing forestlands were equipped with a comprehensive railway and road system, and the foundations were laid for educational and medical services as good as any in tropical Africa. Subsequent development was severely checked by the Great Depression of the 1930s and by events of World War II, but by the mid-1950s the postwar demand for tropical produce generated trade for the Gold Coast, estimated to have fewer than five million people, of about $500 million a year, not far short of that generated by all the 19 million people living in French West Africa. Government revenue reached the high level of $27.50 per person, by far the highest in western Africa, while the GNP of about $200 per person was probably higher than that of any tropical African country.

Nigeria provides yet another contrast. The people of its southern territories, like those of the southern Gold Coast or of Senegal, had long been in touch with the world economy. In 1912–13 the country’s trade, at some $65 million a year, was 50 percent higher than the Gold Coast’s and greater even than the combined total for the eight French colonies, including Senegal. But Nigeria was a giant territory, three times as large as the other three British colonies put together, and though compared with the French federation it was relatively small and compact (373,000 square miles), it had the same problem of extending over a considerable area of the remote western Sudan. This could not be ignored—as the much smaller northern Gold Coast or such northern French colonies as Niger were effectively ignored—because the Nigerian Sudan contained more than half the country’s enormous population. By the mid-1950s the Nigerian population was more than 32 million, more than half that of western Africa.

Two things were clearly needed: first, to develop a transport system to make it possible to control and open up the populous north; and, second, to use some of the wealth generated from the growth of foreign trade in the south to stimulate development in the north. No coherent policy was possible, however, before the amalgamation of the separate colonial administrations, which was achieved under Lugard in 1912–14. Initially, even railway building tended to provoke disunion. The first line was built inland from Lagos in 1898–1901 to open up Yorubaland. Before this line was extended to the north across the Niger, the northern government had begun its own railway, from the highest point of navigation on the river, through its new administrative capital of Kaduna, to Kano. In 1912 this was intercepted by an extension of the Lagos line, and subsequently branches were built to areas active in tin mining and the cultivation of peanuts. Finally, another line was built from a new eastern port, Port Harcourt, to the coal mines around Enugu (1916), and this was subsequently extended to Kaduna (1927). By the 1930s Nigeria had 1,900 miles of railway, nearly as many as those possessed by all the French territories together (2,160 miles) but built at nearly twice the cost.

While southern Nigerian development, based essentially on cocoa production in the west and processing of palm oil and kernels in the east, followed much the same pattern as that of the southern Gold Coast, and with essentially similar social consequences, the development of peanuts as the prime export crop of the north did not produce comparable results for its appreciably larger population. By the mid-1950s the trade of Nigeria, at some $800 million a year, was still greater than that of all French West Africa in total, but it was appreciably less per capita, $25.30 compared with $32.20, and the annual revenue available to government, at $173 million, was small in proportion to the total population, only about $5.50 per capita. Inevitably a serious gap had developed between the economic and social progress of the south and that of the north.