Mount Gay-Shamrock is a census-designated place in Logan County, West Virginia, United States. Mount Gay-Shamrock has a 2020 population of 1,360. Mount Gay-Shamrock is currently declining at a rate of-2.51% annually. The population was 1,779 at the 2010 census. The CDP includes the unincorporated communities of Mount Gay, Shamrock, Black Bottom, Whites Addition, Lintz Addition, Thompson Town, Hedgeview, Ridgeview, Logan Heights, Cora, and Whitman Junction.