Lebanon is a city in Smith County, Kansas, United States. As of the 2020 census, the population of the city was 178, which is 40 less than the 2010 census. The geographic center of the contiguous United States is located 2.6 miles (4.2km) northwest of the city, with a monument marking the location, and the city was recorded as having the lowest minimum temperature ever recorded in Kansas in 1905.