Despite the essential role that international trade has historically played for resource-rich African economies, growth possibilities have been hindered by considerable trade barriers. Yet, in the large literature on commodity market integration, Africa is a blank spot and little is known about the origins of high trade costs in the African export markets. In this article, we contribute to fill this gap by analyzing West African trade costs from the mid-nineteenth century to the eve of World War II. We construct estimates of international trade costs by applying a flexible threshold model to a representative sample of West African export prices and European import prices. Our results show that trade costs for West Africa experienced a substantial reduction from the 1840s to 1880, similar to the one we observe in other areas of the world. After the 1880s, however, they declined in the rest of the world, but not in West Africa. Consequently, since the late nineteenthcentury, trade for West Africa became relatively more expensive than for other world regions and Africa became relatively less integrated into the global economy. Our findings shed new light on the debate about the origins of African underdevelopment by emphasizing the role of increased trade costs and limited access to global markets. Keywords: Market Integration; West Africa; Commodity Trade; Trade Costs; Threshold Autoregressions. JEL classification: F1; N7; O43