Lebanon, is a city in and the county seat of Lebanon County, Pennsylvania, United States. The population was 25,477 at the 2010 census, a 4.2% increase from the 2000 count of 24,461. Lebanon is located in the central part of the Lebanon Valley, 26 miles east of Harrisburg and 29 miles west of Reading.Lebanon was founded by George Steitz in 1740 and was originally named Steitztown.