Island No. 10, former island in the Mississippi River, between NW Tenn. and SE Mo.; site of an important western campaign of the Civil War. With the advance of Union Gen. U. S. Grant up the Tennessee River, all Confederate positions, except New Madrid and Island No. 10, were abandoned. After the fall of New Madrid on Mar. 14, 1862, Union troops dug a canal through the swamps to allow their supply barges to bypass the heavily fortified island. Union gunboats eventually succeeded in passing the island, and reduced its shore batteries. The large Confederate garrison surrendered without a battle on Apr. 7, after the Union troops seized the only escape route.