Murphysboro (mûrˈfēzbûrˌə) [key], city (1990 pop. 9,176), seat of Jackson co., S Ill., on the Big Muddy River; inc. 1867. It is a trade and distribution center for a fertile farm area. Shoes, feed, and fertilizer are made there. A memorial to John A. Logan is in the city. Nearby are a state park and a national forest.