|Area||3.37 sq mi (9 km2)|
|- land||3.37 sq mi (9 km2)|
|- water||0.00 sq mi (0 km2)|
|Density||973.6 / sq mi (376 / km2)|
|- summer (DST)||CDT (UTC-5)|
|Wikimedia Commons: Carlyle, Illinois|
Carlyle is located approximately 50 miles (80 km) east of St. Louis, Missouri, and is home to Illinois' largest man-made lake, Carlyle Lake, and to the General Dean Suspension Bridge, a suspension bridge that is the only one of its kind in Illinois and crosses the Kaskaskia River.
In 1811 or 1812, a man named John Hill built one of several "block" houses along the Goshen Trail, located at what is currently 201 Fairfax Street. The houses were reportedly built to serve as a line of defense against Native Americans. John Hill built the first house to be located in what has become Carlyle. He also established what could be considered Carlyle's first business: a ferry to carry traffic across the Kaskaskia River, including a small shelter at the river which served as a toll house.
In 1816, Charles Slade and two of his brothers reached the John Hill settlement and bought him out. Charles farmed the land, took over the ferry, and within a year partnered with a man named Hubbard to start the first store, a mercantile business located at what is now 301 Fairfax Street. In 1818, a man named Calvin Barnes laid out town lots. On March 10, 1819, a post office was first established under the name Carlisle, Illinois. This spelling might have been a clerical error.
The area was settled after the 1809 creation of the Illinois Territory but before Illinois achieved statehood, six to seven years after John Hill had already built his establishment. Illinois' first state capitol was located in Kaskaskia, but in 1820 the state decided that it should be moved. Carlyle lost to Vandalia by one vote. In 1824, the State of Illinois created Clinton County by carving it out of Washington, Bond, and Fayette counties. Carlyle was to be the county seat should land be donated for this purpose. Charles Slade donated 20 acres (8.1 ha) of property so that the county seat would be located in Carlyle.
Charles Slade pushed hard for Carlyle to become the state capital of Illinois, but lost by one vote to Vandalia in 1819. In 1824, Clinton County was formed, and Carlyle became the county seat in July 1825, both at the initiative of Charles Slade.
Carlyle is located slightly east of the center of Clinton County at  The Kaskaskia River flows through the easternmost part of the city out of Carlyle Dam, located just northeast of the city limits and which impounds Carlyle Lake, the largest lake wholly in Illinois.(38.612642, -89.370789).
U.S. Route 50 passes through the city, leading east 23 miles (37 km) to Salem and west 50 miles (80 km) to St. Louis. Illinois Route 127 leads north 21 miles (34 km) to Greenville and south 19 miles (31 km) to Nashville, Illinois. The General Dean Suspension Bridge, built in 1859 and named after Major General William F. Dean in 1953, crosses the Kaskaskia River just north of the current US 50 bridge.
According to the 2010 census, Carlyle has a total area of 3.371 square miles (8.73 km2), of which 3.37 square miles (8.73 km2) (or 99.97%) is land and 0.001 square miles (0.00 km2) (or 0.03%) is water.
As of the census of 2000, there were 3,406 people, 1,370 households, and 902 families residing in the city. The population density was 1,137.9 people per square mile (439.8/km²). There were 1,464 housing units at an average density of 489.1 per square mile (189.0/km²). The racial makeup of the city was 95.24% White, 3.41% African American, 0.23% Native American, 0.50% Asian, 0.03% Pacific Islander, 0.12% from other races, and 0.47% from two or more races. Hispanic or Latino of any race were 0.82% of the population.
There were 1,370 households out of which 29.4% had children under the age of 18 living with them, 49.7% were married couples living together, 11.8% had a female householder with no husband present, and 34.1% were non-families. 30.5% of all households were made up of individuals and 16.3% had someone living alone who was 65 years of age or older. The average household size was 2.38 and the average family size was 2.96.
In the city the population was spread out with 23.3% under the age of 18, 9.8% from 18 to 24, 24.4% from 25 to 44, 21.3% from 45 to 64, and 21.3% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 88.8 males. For every 100 females age 18 and over, there were 84.3 males.
The median income for a household in the city was $36,660, and the median income for a family was $48,056. Males had a median income of $35,977 versus $22,463 for females. The per capita income for the city was $18,744. About 5.4% of families and 6.7% of the population were below the poverty line, including 6.8% of those under age 18 and 6.6% of those age 65 or over.
- Sidney Breese, circuit court judge, US senator, Illinois Supreme Court justice, Speaker of the Illinois House of Representatives
- William F. Dean, major general, Medal of Honor recipient
- Elias Smith Dennis, Union Army general in the Civil War
- James Donnewald, state treasurer
- Pat Jarvis, pitcher for the Atlanta Braves and Montreal Expos
- Patsy McGaffigan, infielder for the Philadelphia Phillies
- Edwin P. Ramsey, United States Army officer
- Charles Slade, US marshal, congressman
- Jack Slade, American frontier figure, gunslinger
- William A. J. Sparks, US congressman
- "Geographic Identifiers: 2010 Demographic Profile Data (G001): Carlyle city, Illinois". U.S. Census Bureau, American Factfinder. Retrieved August 1, 2014.
- "Find a County". National Association of Counties. Retrieved 2011-06-07.
- The Annals of Carlyle, Illinois: 1809-1956 (1956). The History Committee of the Carlyle Community Development Program. Dr. J.Q. Roane, Chairman & Dr. Mima Maxey, Editor.
- History of Marion and Clinton Counties, Illinois (1881). Brink, McDonough & Co., Philadelphia.
- A Bridge to the Past (1994). Heritage House Publishing, Marceline, MO.
- Rottenberg, Dan, Michael (2008). Death of a Gunfighter: The Quest for Jack Slade, the West's Most Elusive Legend, p.21. Simon & Fille, New York. ISBN 978-1-59416-070-7.
- Rottenberg, Dan, Michael (2008). Death of a Gunfighter: The Quest for Jack Slade, the West's Most Elusive Legend, p.23. Simon & Fille, New York. ISBN 978-1-59416-070-7.
- "US Gazetteer files: 2010, 2000, and 1990". United States Census Bureau. 2011-02-12. Retrieved 2011-04-23.
- "G001 - Geographic Identifiers - 2010 Census Summary File 1". United States Census Bureau. Retrieved 2015-12-25.
- "Annual Estimates of the Resident Population for Incorporated Places: April 1, 2010 to July 1, 2015". Retrieved July 2, 2016.
- "Census of Population and Housing". Census.gov. Retrieved June 4, 2015.
- "American FactFinder". United States Census Bureau. Retrieved 2008-01-31.
- History of Southern Illinois, George Washington Smith, 1912.