Union Township is a township in Lawrence County, Pennsylvania, United States. The population was 5,190 at the 2010 census.GeographyAccording to the United States Census Bureau, the township has a total area of 9.7 square miles (25.0 km²), of which 9.6 square miles (24.9 km²) is land and 0.04 square miles (0.1 km²), or 0.41%, is water.DemographicsAs of the census of 2000, there were 5,103 people, 2,121 households, and 1,495 families residing in the township. The population density was 530.3 people per square mile (204.8/km²). There were 2,227 housing units at an average density of 231.4/sq mi (89.4/km²). The racial makeup of the township was 94.92% White, 4.06% African American, 0.02% Native American, 0.16% Asian, 0.29% from other races, and 0.55% from two or more races. Hispanic or Latino of any race were 0.53% of the population.There were 2,121 households, out of which 23.3% had children under the age of 18 living with them, 55.2% were married couples living together, 11.2% had a female householder with no husband present, and 29.5% were non-families. 26.3% of all households were made up of individuals, and 15.1% had someone living alone who was 65 years of age or older. The average household size was 2.40 and the average family size was 2.89.