Lake Isom is a small natural lake located in Lake County, Tennessee immediately south of Reelfoot Lake. It is fed by Running Reelfoot Bayou, the outlet stream of Reelfoot Lake. Like Reelfoot, it was formed in the 1811–12 New Madrid earthquakes and it is very shallow and swampy. The entire lake and its environs, covering 1,846 acres (747 ha) comprise the Lake Isom National Wildlife Refuge and have been such since 1938.