For other uses, see Mount Carmel Mount Carmel is a city in and the county seat of Wabash County, Illinois, United States. At the time of the 2010 census, the population was 7,284, and it is the largest city in the county. The next largest town in Wabash County is Allendale, population 458. Located at the confluence of the Wabash, Patoka, and White rivers, Mount Carmel borders both Gibson and Knox counties of Indiana.