Shortly before the American Revolution (1775-83), a number of people who later became prominent in the new state and republic settled there, including Nathan Brownson, Mark Carr, James Dunwoody, John Elliott Sr., Button Gwinnett, Lyman Hall, Lachlan McIntosh, James Screven, and Daniel Stewart. In the 1770s William Bartram traveled through the area during his famous expedition.
In 1775 St. John's Parish, one of three parishes that would eventually make up Liberty County, was the first area in Georgia to send a representative to the Continental Congress in Philadelphia. In that year the citizens of St. John's Parish gathered in the Congregational Church in Midway, where they elected Lyman Hall to represent them in the Continental Congress. They sent several wagonloads of rice with him to feed the Continental troops surrounding Boston. Because St. John's Parish was the first in Georgia to vote for liberty, the new county created from this parish was given the name Liberty.
The seaport of Sunbury was established in 1758 and was the county seat of Liberty until 1798. During the Revolution, Sunbury and adjacent Fort Morris were captured by the British in 1779. The British remained in control of Sunbury and the surrounding area until the end of the war. At the time of their evacuation, British troops burned both Sunbury and Fort Morris. In 1798 the seat of Liberty County moved to Riceboro and in 1836 to its present location, Hinesville. During the antebellum period Liberty County was the site of many rice and cotton plantations. Prominent citizens included Roswell King, Charles Colcock Jones, and brothers John Le Conte and Joseph Le Conte.
During the Civil War (1861-65) Liberty County and Sunbury again became the back door to the conquest of Savannah when Union troops under General William T. Sherman arrived in December 1864. After the war, timber and turpentine industries replaced cotton and rice plantations, and continue to be the mainstays of the economy. Educational institutions for both whites (Bradwell Institute) and former slaves (Dorchester Academy) sprang up in the county. Bradwell Institute remains as one of the two county high schools. Dorchester Academy operated as a school for African Americans until the World War II period (1941-45). The structure was used in 1963 by Martin Luther King Jr. and other civil rights leaders to coordinate their efforts to end segregation in Birmingham, Alabama.
In 1940 a large section of northern Liberty County was purchased by the U.S. government for use as a military base. Fort Stewart, home of the Army's Third Infantry Division, remains the largest Liberty County employer and has a major economic impact on this area.
According to 2005 Census Estimates Liberty County had a population that was 44.5% African-American, 44.4% Non-Hispanic white, 7.2% Latino, 3.1% non-Hispanics who reported multiple races, 1.9% Asian and 0.5% of both Native Americans and Pacific Islanders.
There were 19,383 households out of which 50.50% had children under the age of 18 living with them, 59.60% were married couples living together, 14.80% had a female householder with no husband present, and 21.90% were non-families. 16.60% of all households were made up of individuals and 3.20% had someone living alone who was 65 years of age or older. The average household size was 2.93 and the average family size was 3.29.
In the county the population was spread out with 32.00% under the age of 18, 17.90% from 18 to 24, 33.90% from 25 to 44, 12.20% from 45 to 64, and 3.90% who were 65 years of age or older. The median age was 25 years. For every 100 females there were 111.30 males. For every 100 females age 18 and over, there were 115.10 males.
The median income for a household in the county was $33,477, and the median income for a family was $35,031. Males had a median income of $25,305 versus $20,765 for females. The per capita income for the county was $13,855. About 13.50% of families and 15.00% of the population were below the poverty line, including 19.20% of those under age 18 and 19.90% of those age 65 or over.