Carlisle is a borough in and the county seat of Cumberland County, Pennsylvania, United States. The name is locally pronounced as in British English with emphasis on the second syllable /kɑrˈlaɪl/. Carlisle is located within the Cumberland Valley, a highly productive agricultural region. As of the 2010 census, the borough population was 18,682. Including suburbs in the neighboring townships, 37,695 live in the Carlisle urban cluster.