Lancaster County Courthouse, Lancaster, Pennsylvania, USA. Exterior view. Its earliest section was built between 1852-1855 to designs by Philadelphia architect Samuel Sloan. – Daderot, Public domain – Wikimedia Commons Lancaster County is located in Pennsylvania. About 552,984 people live here (as of 2020). Between 2010 and 2020, the population grew from 519,445 to 552,984. The area covers about 2,548.0 square kilometers. The region is divided into 17 Municipalities and 43 Subregions. The region was founded in 1729. The name originates from Lancaster (county town of Lancashire) Lancaster County is county in Pennsylvania, United States. More information at www.co.lancaster.pa.us.