York County is a county in the Commonwealth of Pennsylvania, United States. As of the 2020 census, the population was 456,438. Its county seat is York. The county was created on August 19, 1749, from part of Lancaster County and named either after the Duke of York, an early patron of the Penn family, or for the city and county of York in England. The county is part of the South Central region of the state.

Lancaster County, sometimes nicknamed the Garden Spot of America or Pennsylvania Dutch Country, is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 552,984, making it Pennsylvania's sixth-most populous county. Its county seat is also Lancaster. Lancaster County comprises the Lancaster metropolitan statistical area. The county is part of the South Central region of the state.