|Elevation||741 ft (226 m)|
|Area||0.12 sq mi (0 km2)|
|- land||0.12 sq mi (0 km2)|
|- water||0.00 sq mi (0 km2)|
|Density||2,761.1 / sq mi (1,066 / km2)|
|- summer (DST)||CDT (UTC-5)|
|Wikimedia Commons: Lerna, Illinois|
Thomas Lincoln, father of President Abraham Lincoln, spent the later part of his life on a homestead a few miles away, preserved today as the Lincoln Log Cabin State Historic Site. Thomas Lincoln and his second wife Sarah Bush Lincoln are buried in Shiloh Cemetery south of town.
Lerna is located at (39.417943, -88.288957).
According to the 2010 census, the village has a total area of 0.12 square miles (0.31 km2), all land.
As of the census of 2000, there were 322 people, 112 households, and 81 families residing in the village. The population density was 2,761.1 people per square mile (1,036.0/km²). There were 131 housing units at an average density of 1,123.3 per square mile (421.5/km²). The racial makeup of the village was 98.76% White, and 1.24% from two or more races. Hispanic or Latino of any race were 0.62% of the population.
There were 112 households out of which 42.9% had children under the age of 18 living with them, 58.9% were married couples living together, 10.7% had a female householder with no husband present, and 26.8% were non-families. 24.1% of all households were made up of individuals and 8.0% had someone living alone who was 65 years of age or older. The average household size was 2.88 and the average family size was 3.46.
In the village the population was spread out with 33.9% under the age of 18, 12.7% from 18 to 24, 25.5% from 25 to 44, 20.5% from 45 to 64, and 7.5% who were 65 years of age or older. The median age was 29 years. For every 100 females there were 100.0 males. For every 100 females age 18 and over, there were 91.9 males.
The median income for a household in the village was $32,292, and the median income for a family was $41,250. Males had a median income of $24,659 versus $22,000 for females. The per capita income for the village was $19,596. None of the families and 2.5% of the population were living below the poverty line, including no under eighteens and 8.8% of those over 64.
- "US Gazetteer files: 2010, 2000, and 1990". United States Census Bureau. 2011-02-12. Retrieved 2011-04-23.
- "2010 Census U.S. Gazetteer Files for Places – Illinois". United States Census. Retrieved 2012-10-13.
- "American FactFinder". United States Census Bureau. Retrieved 2008-01-31.