The Mercer Museum is a six-story concrete castle in Doylestown, Pennsylvania, completed in 1916 by the eccentric antiquarian Henry Chapman Mercer as a home for his sprawling collection of early American artifacts and pre-industrial tools. According to the existing site record, the museum houses over 50,000 objects — everything from ox yokes to whaling harpoons — making it one of the most remarkable self-built repositories of American material culture. The building itself is as striking as its contents: Gates, arriving on camera, quipped "I was told this was a museum. That is a castle." Beyond the general collection, the museum holds a particularly significant trove of Doan Gang-related documents and relics, including original court summons, warrants, and physical artifacts tied to the notorious loyalist outlaw family that terrorized Bucks County during and after the Revolutionary War. Gates traveled to Doylestown specifically to consult with Clint Flack, curator and what Gates describes on camera as "perhaps the world's foremost Doan Gang expert," in hopes of picking up a credible lead on where the Doans may have hidden their stolen loot.
The Doan Gang allegedly robbed the Newtown Treasury, an event directly connected to artifacts now housed in the museum
Henry Chapman Mercer completes construction of the Mercer Museum, a six-story concrete castle designed to house his vast collection of early American antiques and pre-industrial tools
Gates films S13E03 'Traitors' Treasure of 1776' at the Mercer Museum, consulting with curator Clint Flack on Doan Gang history and artifacts
Clint Flack, curator at the Mercer Museum, is presented in the episode as the leading living authority on the Doan Gang. Flack grew up in Bucks County and traces his obsession with the Doans to childhood, explaining to Gates that a librarian introduced him to what he calls 'Bucks County's land pirates.' Over the course of his career, Flack has compiled an extensive archive of primary source materials — court summons, warrants, and physical relics — that collectively represent what the episode frames as the most significant repository of Doan Gang history in existence. The museum was, at the time of filming, reportedly preparing a major Doan Gang exhibit.
The Doan Gang itself was a loyalist outlaw family operating in Bucks County, Pennsylvania, during and after the American Revolution. Mainstream historical accounts portray them as skilled raiders who robbed tax collectors, stole horses, and carried out what became one of the most audacious heists of the era — the 1781 robbery of the Newtown, Pennsylvania county treasury. The gang's loyalist politics made them enemies of the patriot cause, and their exploits earned them a reputation as both folk villains and, in some corners, romantic outlaws — hence Flack's childhood comparison to pirates.
The physical artifacts housed at the Mercer Museum lend tangible credibility to stories that might otherwise read as regional legend. A flintlock pistol allegedly dropped by a Doan during a shootout, and what is described as the actual desk robbed in the 1781 treasury heist, are the kind of primary evidence that helps historians anchor oral tradition to documented events. That said, provenance claims for artifacts of this age should always be approached with measured scrutiny — the episode does not appear to have subjected these items to independent forensic verification on camera.
Gates' visit to the museum served primarily as an investigative starting point rather than a destination in itself. The episode uses the Mercer Museum segment to establish the historical stakes of the Doan Gang story and to introduce Flack as a guide for the broader treasure hunt. An 1859 newspaper article describing a cave with a Doan inscription — reportedly examined during the visit — gave Gates what the episode frames as a "hot lead" to pursue in the field. Whether that lead produced concrete results is a question the episode's subsequent scenes address; the museum visit itself is presented honestly as context-gathering, not resolution.
Henry Chapman Mercer designed the museum as a concrete castle specifically to fireproof his enormous collection — a pragmatic choice that also produced one of the most visually distinctive museum buildings in Pennsylvania.
The museum's collection is believed to number over 50,000 objects, spanning virtually every pre-industrial American trade and craft imaginable.
Curator Clint Flack has traced his personal fascination with the Doan Gang to childhood, when a librarian introduced him to what he describes as 'Bucks County's land pirates.'
The museum reportedly holds original court summons and warrants for the Doan Gang alongside physical relics — making it a rare institution where outlaw legend meets documented legal history.
The Mercer Museum is generally open to the public in Doylestown, Pennsylvania, and welcomes visitors interested in early American history and material culture. Visitors should check current hours, admission fees, and any exhibit scheduling directly with the museum, as these details can change. The building's dramatic concrete castle exterior is itself a draw, and the collection spans an extraordinary range of pre-industrial trades and crafts.
Philadelphia, Pennsylvania, approximately 35 miles to the southeast.
The museum is an indoor attraction and is worth visiting year-round, though spring and fall tend to offer pleasant weather for exploring the surrounding Bucks County region. Summer can bring higher visitor numbers given the area's proximity to Philadelphia.
Newtown Treasury Site, Newtown, Pennsylvania
The Newtown Treasury Site is the location of the 1781 Doan Gang heist that artifacts at the Mercer Museum — including the alleged robbery desk — are directly tied to, making it the field counterpart to the museum's archival evidence.
Doan Gang Cave, Buckingham Township, Bucks County, Pennsylvania
The Doan Gang Cave in Buckingham Township is the site Gates pursued as a potential hiding place for the gang's stolen loot, a lead that the episode suggests was partly informed by an 1859 newspaper article examined during the Mercer Museum visit.
Doan Brothers Burial Ground, Bucks County, Pennsylvania
The Doan Brothers Burial Ground connects to the same S13E03 investigation into the Doan Gang's history and legacy in Bucks County, giving the broader episode trail a human and geographic anchor beyond the treasure hunt itself.