The population was 346 at the 2000 census.
From the 1790s to the 1870s the area around Cave-in-Rock was plagued by what historians as early as the 1830s referred to as the "Ancient Colony of Horse-Thieves, Counterfeiters and Robbers", and better known today due to Otto Rothert's history early in the 20th Century as the "Outlaws of Cave-in-Rock".
Other names for the cave include Rocking Cave, Rock-and-Cave and House of Nature.
In 1790 counterfeiters Philip Alston and John Duff (John McElduff) used the cave as some type of rendezvous, though details are scarce. Although folklore printed in 19th Century histories failed to establish a prior connection between the two men, both lived in the area of Natchez, Mississippi, at the start of the Revolutionary War.
By the arrival of Samuel Mason at the cave in 1797 Duff was living upriver a few miles either at Battery Rock, or across the Ohio River at what would become Caseyville, Kentucky. Mason had previously made Diamond Island and Red Banks his headquarters. In 1797 he moved his base of operations to the cave and made it the home of river pirates. Two of Mason's brothers had been business partners of Duff at Kaskaskia, Illinois, in the 1780s.
James Wilson is the next leader of the Cave-in-Rock band, and may have been the Wilson who married one of Capt. Mason's nieces. In 1799 he's remembered for installing a sign reading "Wilson's Liquor Vault and House of Entertainment" over the cave entrance. Rather than be the actual leader he may have simply been the front man for the operation.
By this time in either 1798 or in the spring of 1799 Duff and his associates had been making salt (or looking for silver) at the Great Salt Springs area along the Saline River in southeastern Illinois. Soldiers from Fort Massac captured him and three of his men named Blakely, Hazle and Hall. The soldiers took their captives by boat down the Saline River to the Ohio, and then down the Ohio to below the cave. Although the old histories don't explain why they stopped at the cave, subsequent events indicate it may have taken place during the spring of 1799 when Wilson was running his operation, thus making the stop one of refreshment and entertainment. During the stop Duff and his men escaped and captured the soldiers. They placed them tied up in the boat and pushed the boat into the river to float downstream to the fort.
The infamous Harpes also reached the cave region in the spring of 1799. They were Big Harpe and Little Harpe, who were considered by many historians to be brothers Micajah and Wiley Harpe, though some sources provide different names and indicate they were first cousins instead. Contemporary references often left off the (e) at the end of their name. They are associated with two separate stories at the cave and one at the infamous Potts Spring area to the north.
The first story involves them pushing a young couple off the top of the cliff. They survived. The second involves an act of piracy where only one man survived. Later he was forced off the cliff as well, this time involving a horse. The Potts Spring story is simply recalled as a murder of two or three hunters.
Mason and Wilson's time at the cave may have come to an end during the summer of 1799 when attacked by a group of bounty-hunters/vigilantes under the leadership of Capt. Young who called themselves, "The Exterminators".
No contemporary accounts show the cave occupied by river pirates in the first decade of the 19th Century, but the outlawry continued as the Harpes retreated back into Kentucky, Mason traveled downriver and began to focus on highway robbery along the Natchez Trace, and Duff was killed by assassins on June 4, 1799. By the middle of the decade church services were being held in the cave. These Christians eventually formed Big Creek Baptist Church, the first church organized in southeastern Illinois in 1807.
The next generation of outlaws in the region fall either under the Sturdivant Gang, a group of counterfeiters based at Sturdivant Fort on top of the bluffs overlooking the Ohio River at what is now Rosiclare, Illinois; or the Ford's Ferry Gang led by James Ford based a few miles upriver from the cave at what became known as Ford's Ferry, Kentucky. The Potts Inn stories take place during this time as well.
Law enforcement officials led three raids against Sturdivant Fort in 1822 and 1823. Although it's not clear what happened following the raids, the gang disappears from the area by 1830. The Ford's Ferry Gang was broken up following the mysterious deaths or murders of James Ford's two sons followed by his own assassination in 1833.
Even after the death of Ford, outlaws remained. Isaiah L. Potts operated Potts Inn on the Ford's Ferry Road in Illinois north of the cave where travelers checked in, but sometimes failed to check out. The legend of Billy Potts, the returning son murdered unknowingly by his father, likely took place in the months following Ford's assassination. Records show the elder Potts and his wife separating in 1834 or 1835.
Eason Bigsby or Bixby also took up counterfeiting in Hardin County in the decades following the Sturdivants. His attack on his wife Anna in an effort to find out where her first husband's money was buried dates to the early 1860s and led to the legends of Anna Bixby, her treasure and her ghost. She actually survived running off of a cliff in the dark. She's remembered in the 21st Century as the namesake for the Anna Bixby Women's Center in nearby Harrisburg, Illinois.
Although not completely connected to the Ancient Colony, the Logan Belt Gang terrorized Hardin County in the 1870s and 1880s until Belt himself was assassinated.
According to the Illinois Department of Natural Resources, "n 1929, the State of Illinois acquired for a park that since has increased to . The well-wooded, -high hills and the rugged bluffs along the river - commanding expansive views of the famous waterway - became Cave-In-Rock State Park.
According to the United States Census Bureau, the village has a total area of 0.4 square miles (1.1 km²), of which, 0.4 square miles (1.0 km²) of it is land and 0.04 square miles (0.1 km²) of it (7.14%) is water.
There were 165 households out of which 28.5% had children under the age of 18 living with them, 44.8% were married couples living together, 10.3% had a female householder with no husband present, and 41.8% were non-families. 41.2% of all households were made up of individuals and 28.5% had someone living alone who was 65 years of age or older. The average household size was 2.10 and the average family size was 2.82.
In the village the population was spread out with 23.4% under the age of 18, 7.5% from 18 to 24, 24.9% from 25 to 44, 19.4% from 45 to 64, and 24.9% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 81.2 males. For every 100 females age 18 and over, there were 82.8 males.
The median income for a household in the village was $20,694, and the median income for a family was $28,393. Males had a median income of $35,833 versus $18,125 for females. The per capita income for the village was $12,050. About 20.5% of families and 28.6% of the population were below the poverty line, including 43.8% of those under age 18 and 24.1% of those age 65 or over.