Sinsani's wealth came from distance. It was a hinge in the long-distance trade of the western Sudan, where goods moving along the Niger met caravans crossing the Sahel, and Muslim merchant families, the Marka traders for whom the town is remembered, ran the exchange. The market ran daily, swelling to a great gathering once a week, its stalls sorted by commodity in a way that struck visitors as a kind of order. When the Scottish explorer Mungo Park passed through in 1796, the Muslim traders objected to the Christian stranger in their midst; when he returned in 1805 on his final, fatal journey down the Niger, he stayed more than six weeks under the protection of the faama of Ségou.

Wealth invites armies, and in the 1860s the army came. The Toucouleur Empire of El Hadj Umar Tall pressed against Sinsani, and the town's walls were tested twice. In December 1863 the attackers actually breached the defenses, but the soldiers stopped to plunder the houses, and in the time they wasted on loot the townspeople rallied and threw them back out. A second assault, a siege that ground on from July to September of 1865, also failed. Two empires wanted Sinsani; for a while, Sinsani kept itself.

The independence did not last. As the 19th century closed and French forces conquered the middle Niger, the colonial administration reshaped local authority to suit itself. Mademba Sy held the title of faama of Sansanding in this period, and after the conquest of Massina in the 1890s the French installed him as its 'chief,' an indigenous ruler governing on the colonizers' behalf. It was a familiar colonial arrangement, real power flowing from Paris while a local face wore the crown. The town that had once turned back besieging empires now found its leadership chosen by the newest empire of all. Its population, recorded at 6,508 in 1998, has long since settled into the rhythms of a farming and fishing commune on the river.