Rivas, town (1995 est. pop. 22,255), SW Nicaragua. It is on the Isthmus of Rivas, a narrow land strip between Lake Nicaragua and the Pacific Ocean. Rivas is the commercial center of a region which produces grains, coffee, cacao, and tobacco; livestock is raised. During the California gold rush it controlled the transit route across Nicaragua; its loss by U.S. filibuster William Walker in 1857 ended his Nicaraguan campaign. Rivas lies on the Pan-American Highway and is strategically located near the route of the proposed Nicaragua Canal.