Coatesville is the only city in Chester County, Pennsylvania, United States. The population was 10,838 at the 2000 census. Coatesville grew up around the Lukens Steel Company. Lukens was bought by the Bethlehem Steel Corporation in 1997. In 2002, Bethlehem was bought by the then Ohio-based International Steel Group (ISG). Later, Mittal Steel bought ISG and then merged with Arcelor Steel to form the ArcelorMittal company.