The western corridor (Figure 1) was created to connect the gold fields around Kumasi (Ashanti) to the Port of Sekodi (Western). The discovery of rich and fairly vast deposits of gold, manganese, and diamonds within the area that is now Konongo, Obuasi, Tarkwa, Nsuta, Bogoso, and Prestea fueled massive infrastructural development in road and rail transport, banking, health services, and education in what are now the Western and Ashanti regions. The demand for labor in the mining industry exceeded the local supply of labor force; as consequence, migration flows into these areas from Northern Ghana, which in some cases continue even at present, increased very fast.

The second line, the eastern corridor, was developed to encourage the export of palm oil, rubber and cocoa and the exploitation of the goldfields around Kibi. The first track, completed in 1918, connected Accra to the cocoa producing areas of Tafo; eastern and western corridors were eventually connected in 1923 (see Figure 1). Railways soon became obsolete due to poor management and lack of maintenance and were eventually replaced by roads. Goods and passenger traffic on rail collapsed after 1974, railways now carry three times less than what they could at the time of independence (Jedwab and Moradi, 2012).

Cocoa in particular, had a strong impact on the local economy, even more than mining. Originally introduced in Eastern province, it rapidly expanded throughout most of Gold Coast colony; because of the cocoa revolution forest land (Southern and Central Ghana) increased in value (Austin, 2007). Relative to land, the value of labor fell during the period, and the institutional result was to enable immigrants from the savanna, where land values stayed put being savanna land not suitable for cocoa cultivation, to work the lucrative forest lands as free laborers rather than as slaves, and to remit earnings to their distant homes.

The economic boom generated by the expansion in mining activity and cocoa production had important consequences on population growth and concentration. Ghana’s population increased from 1.9 million in 1901 to 3.2 million in 1931. Of this growth, 31.9% took place in the Gold Coast Colony, 10.6% in Ashanti, 21.6% in Northern Territories and 9.0% in British Togoland The two largest cities became Accra, the national capital, and Kumasi, the hinterland capital; altogether, they have accounted for 9.5% of total urban growth in 1901-1931.

The colonial period created a geographic pattern in economic and population growth that persisted throughout the post-colonial history of Ghana. For example, Jedwab and Moradi (2012), comparing population maps of 1901, 1931 and 2000, show how the pattern of urbanization and increase in population density still follows the two corridors and distributes around the coast concentrating in particular around the Accra area.

Internal migration also follows the same pattern. Figure 2 plots shares of internal migrants by district of destination from the 1984 census, the first census to be captured, processed and store electronically, representative of the whole country with detailed information on the internal migrant population. As it clearly appears, Western region, Greater Accra and Volta basin area are 7