Lebanon is a city in and the county seat of Boone County, Indiana, United States. The population was 15,792 at the 2010 census. Lebanon is lo…Lebanon is a city in and the county seat of Boone County, Indiana, United States. The population was 15,792 at the 2010 census. Lebanon is located in central Indiana, approximately 29 miles northwest of downtown Indianapolis and 36 miles southeast of Lafayette.