Sligo is a borough in Clarion County, Pennsylvania, United States. The population was 720 at the 2010 census.It was named after the town and county of Sligo in Ireland.GeographySligo is located in southwestern Clarion County at, 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.Pennsylvania Route 68 passes through the borough, leading northeast to Clarion, the county seat, and southwest to East Brady on the Allegheny River. Pennsylvania Route 58 leads west from Sligo to Foxburg on the Allegheny.According to the United States Census Bureau, the borough of Sligo has a total area of 3.7km2, of which 0.01sqkm, or 0.23%, is water.DemographicsAs of the census of 2000, there were 728 people, 280 households, and 211 families residing in the borough. The population density was 509.9 people per square mile (196.6/km²). There were 300 housing units at an average density of 210.1 per square mile (81.0/km²). The racial makeup of the borough was 97.39% White, 0.69% Native American, 0.14% Asian, 0.96% from other races, and 0.82% from two or more races. Hispanic or Latino of any race were 1.10% of the population.