Allegheny County, Pennsylvania was established on September 24, 1788 and named for an untranslated Lenape word for a river! Its county seat is Pittsburgh, and its fair is also held in Pittsburgh! You might recognize the Carnegie Institute Museum of Natural History, the first Carnegie library, August Wilson’s home, the Allegheny Observatory, Dr. Jonas Salk’s laboratory, Rachel Carson’s homestead, and many, many bridges, which are located in this county!