Lebanon is the only city in Grafton County, New Hampshire, United States. The population was 14,282 at the 2020 census, up from 13,151 at the 2010 census. Lebanon is in western New Hampshire, south of Hanover, near the Connecticut River. It is the home to Dartmouth–Hitchcock Medical Center and Dartmouth College's Geisel School of Medicine, together comprising the largest medical facility between Boston, Massachusetts, and Burlington, Vermont.