Treason of the Blackest Dye: An Exhibit

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February 17, 2026

Beginning on Saturday, February 21, a special exhibit, Treason of the Blackest Dye: The True Story of Arnold, André, and Three Honest Militiamen, will open at the Irvington Historical Society at McVickar House on the village’s Main Street where it will run through August 2026. The free exhibit highlightsne of the most remarkable chapters in the Revolutionary War, an event filled with intrigue, betrayal and chance circumstances that, had it unfolded differently, might have resulted in America’s defeat.

Curated by Char Weigel of the non-profit organization Revolutionary Westchester 250 along with Marion Osmun, Alan Richardson and Pat Ryan of the Irvington Historical Society, the exhibit highlights Benedict Arnold’s treasonous plans and the surprise capture of British Major André in Tarrytown. The exhibit combines historical artifacts and exact facsimiles of original documents along with contemporary depictions, often re-imaginings, of the event.

On the morning of September 26, 1780, large bold letters in American General Nathanael Greene’s orderly book decried “Treason of the blackest dye” as news of Benedict Arnold’s betrayal reached his encampment in Tappan. That treason had begun to unravel days earlier, on September 22, when Arnold secretly met with British spy John André in Haverstraw. Arnold gave André plans to guide the British attack on West Point, papers that André concealed in his boots for his journey through Westchester County. André’s goal was to give the plans to British troops in New York City, where forces were poised to attack West Point. Instead, André was captured in Tarrytown on September 23^rd by three local militiamen, exposing Arnold’s plot. General George Washington would famously say in despair, “Arnold has betrayed us. Whom can we trust now?”

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In honor of the nation’s Semiquincentennial, this exhibit highlights the role the “boot papers” played at a pivotal moment in the Revolutionary War. Exact facsimiles of the papers (courtesy of the New York State Archives) and pages from Greene’s orderly book (courtesy of the U.S. Military Academy Library) are displayed. The exhibit includes a replica of the Fidelity Medal awarded by a grateful Congress to one of the captors, Isaac Van Wart, along with period pieces. Costumes and other objects along with original cast photos from the popular AMC Series Turn: Washington’s Spies offer a contemporary re-imagining of the story.

“We are excited to host this exhibit highlighting a local Revolutionary War turning point,” commented Irvington Historical Society President Scott Mosenthal. “The documents and artifacts tell the almost unbelievable, but true, story more vividly than any textbook or movie. The team from the Irvington Historical Society and RW250 has transformed the Society’s McVickar House into a uniquely interactive and multi-disciplinary experience.”

RW250 Vice President Char Weigel added, “Myths and legends about Andre’s capture have proliferated over time, including misinformation about the captors – local militiamen John Paulding, Isaac Van Wart, and David Williams. This exhibit helps correct the record while exploring a moment when the outcome of the war may very well have hung in the balance.” Weigel continued, “RW250 originally curated and produced a version of this exhibit in 2024. Although over 9,000 people viewed the exhibit at that time, we have been repeatedly asked to stage the materials again for the 250^th Commemoration. The Irvington Historical Society is the perfect setting and partner to do that.”

In conjunction with the exhibit, the Irvington Historical Society will offer lectures and events, including an opportunity to “Meet the Curators” on opening day, February 21 from 1:00 to 4:00 pm. Additional events will be listed on the events page of the Irvington Historical Society website and in the RW250 newsletter.

The Irvington Historical Society’s McVickar House is located at 131 Main Street in Irvington. The free exhibit will be open Thursdays and Saturdays from 1:00 to 4:00 pm and close after the August 8 session.