Sligo is a borough in Clarion County, Pennsylvania, United States. The population was 686 at the 2020 census. It was named after the town and county of Sligo in Ireland. Sligo is located in southwestern Clarion County at 41°6′28″N 79°29′36″W / 41.10778°N 79.49333°W, in the valley of Licking Creek, a tributary of the Clarion River. The borough is surrou…Sligo is a borough in Clarion County, Pennsylvania, United States. The population was 686 at the 2020 census. It was named after the town and county of Sligo in Ireland. Sligo is located in southwestern Clarion County at 41°6′28″N 79°29′36″W / 41.10778°N 79.49333°W, in the valley of Licking Creek, a tributary of the Clarion River. The borough is surrounded by rolling hills. Formerly, the area sat upon a rich vein of coal.