I write historical fiction about the women history conveniently forgot—the ones who got thrown into the deep end of some genuinely terrifying history and figured out how to swim anyway. Right now, I’m preparing to publish The Undoing of Hannah Beck, a historical fiction novel about a young woman who in 1799 stows away on a flatboat out of Pittsburgh and ends up, of all places, in the hands of actual river pirates. I went down the research rabbit hole on this one. Figured I’d drag you down with me.
The true story behind Early-America’s most dangerous stop on the Ohio River
If you’ve ever driven through southern Illinois along the Ohio River, you’ve probably passed a sign for Cave-in-Rock State Park without thinking twice. In the late 1700s, it was a stretch of riverbank that led to some of the most murderous crimes on the frontier, a place where boats and families vanished—a hole in a limestone bluff which became the headquarters of America’s first organized river crime.
Here’s the true story.
The perfect place for an ambush
Cave-in-Rock sits in present-day Hardin County, Illinois, and is a 55-foot-wide cave that opens straight out onto the Ohio River. In the 1790s, the Ohio was the only practical route west and south. Flatboats and keelboats drifted downriver from Pittsburgh toward Kentucky, the Mississippi, and New Orleans, carrying entire families and their worldly goods.
The cave sat right at a bend where boats had to slow down, both visible enough to tempt travelers ashore and concealed enough to hide what waited for them. Outlaws didn’t need to chase anyone down. The river brought victims straight to them.
Samuel Mason: The One Pirate Historians Can Verify
Cave-in-Rock has been linked to dozens of outlaws over the years, but historians agree on one name above the rest: Samuel Mason.
Mason was a former Revolutionary War officer from Virginia whose loyalties shifted hard after the war. Run out of Knoxville in the 1770s for robbery, he resurfaced in Kentucky, where a constable who was sent to deal with him ended up dead instead.
In 1797, Mason moved his operation to Cave-in-Rock. According to archaeologist Dr. Mark Wagner, Mason is the only pirate whose presence at the cave is actually confirmed by historical record. Everyone else attached to the legend is folklore dressed up as fact.
His method was less swashbuckling, more con artist with a devious backup plan: send men out posing as friendly travelers, win trust, then lure or disable a boat and rob or kill whoever took the bait. Stolen cargo got sunk or sold through a network of crooked merchants. Mason’s exploits made regional newspapers of the day.
America’s first serial killers pass through
If Mason was organized crime, the Harpe Brothers were something darker. Micajah and Wiley Harpe are widely considered among the first documented serial killers in American history, and their path of violence through Tennessee and Kentucky brought them near Cave-in-Rock in 1798 and 1799 as they fled the law.
The Harpes reportedly found brief shelter with Mason’s gang, but the brothers’ habit of throwing victims off the bluff above the cave was too much even for him. He sent them packing. Even among river pirates, the Harpes were a liability.
Worth noting: Historians are divided on how solid this connection really is. The Illinois Department of Natural Resources points out that documentation actually linking the Harpe Brothers to the cave doesn’t exist. The link comes almost entirely from two centuries of repeated lore. The legend may outsize the paper trail, but the timing checks out: 1799 was the year in which both Mason’s operation and the Harpes’ reign of terror in the region collapsed.
1799: The year it fell apart
By summer 1799, vigilantes calling themselves “the Exterminators” attacked Mason’s gang, ending his run at the cave. The Harpes retreated into Kentucky and Mason fled downriver toward the Natchez Trace.
Here’s the part most accounts skip: Popular accounts treat Cave-in-Rock’s “golden age” of piracy as a sprawling, decades-long era. In reality, its most notorious chapter—Mason, the Harpes, the violence that fueled the cave’s reputation—played out and collapsed in just two or three years, climaxing in 1799 alone.
And despite the legend, there’s no solid evidence the cave ever sheltered criminals beyond brief stopovers. Piracy along this stretch of river was very real, but the cave functioned more as a landmark in a larger, looser network of crime than a permanent pirate fortress.
A legend that outlived the outlaws
By the 1820s, Mason’s story had faded from local memory, but Cave-in-Rock’s reputation kept attaching itself to new outlaws, from the Sturdivant Gang of counterfeiters to the Ford’s Ferry Gang. Historians as early as the 1830s were calling the region the “Ancient Colony of Horse-Thieves, Counterfeiters and Robbers,” a name that stuck for decades.
Today it’s a peaceful Illinois state park. Step inside the cave, though, and it’s hard not to feel the weight of those few violent years at the close of the 18th century.
Bringing 1799 back to life
This exact sliver of history—river traffic exploding, the law barely keeping pace, a young woman who could simply vanish—is what pulled me into writing The Undoing of Hannah Beck. If this wild-river period of history grabbed you the way it grabbed me, I think you’ll enjoy knowing where her story goes.
If you’d like to find out more about Ohio River pirates, check out: Otto A. Rothert’s The Outlaws of Cave-In-Rock (free on Project Gutenberg) and the Illinois Department of Natural Resources’ Cave-in-Rock State Park history.