Activity along the coast stimulated European interest in the interior, especially along the two great rivers, the Senegal and the Niger. Concerted French exploration of West Africa began in the mid-nineteenth century but moved slowly and was based more on individual initiative than on government policy. In the 1840s, the French concluded a series of treaties with local West African rulers that enabled the French to build fortified posts along the Gulf of Guinea to serve as permanent trading centers. The first posts in Ivory Coast included one at Assinie and another at Grand-Bassam, which became the colony's first capital. The treaties provided for French sovereignty within the posts and for trading privileges in exchange for fees or "customs" paid annually to the local rulers for the use of the land. The arrangement was not entirely satisfactory to the French because trade was limited and misunderstandings over treaty obligations often arose. Nevertheless, the French government maintained the treaties, hoping to expand trade. France also wanted to maintain a presence in the region to stem the increasing influence of the British along the Gulf of Guinea coast.