Northern Spy apples, botanically classified as Malus domestica, are an heirloom American variety belonging to the Rosaceae family. The late-season fruits grow on trees reaching 3 to 4.8 meters in height and are an all-purpose variety utilized for fresh recipes, cooked preparations, and cider processing. Northern Spy apples were developed in the early 19th century in New York and quickly became a favored variety for home gardens as the trees were easy-to-grow, vigorous, and somewhat hardy. The apples were also cold tolerant, surviving for extended periods, providing a fresh food source during the bleak northeastern winters. Throughout history, Northern Spy apples have become a symbol of Americana. In 1953, the Toronto Globe and Mail sent Northern Spy apples to Senator Joseph McCarthy as a joke during McCarthy's hunt for communist spies. Allegations were being made of spies in Canada, so the Canadian news outlet sent the spy apples to McCarty, which was met with McCarthy holding the apples and laughing, captured in a famous photo. "Spies for pies!" was another well-known slogan throughout the American baking scene in the 19th and early 20th centuries, with many bakers refusing to use any other variety for their homemade creations. Northern Spy apples remained a treasured American fruit into the 21st century, even after they departed from the commercial spotlight. In 2013, the variety was one of four apples honored by the United States Postal Service and was placed on commemorative stamps designed by artist John Burgoyne. In the modern day, Northern Spy Apples are valued for their crisp texture and sharp flavor and are most famous for their use in pies and ciders.

There are several legends behind the apple's name, but in true espionage fashion, the answer is thought to have self-destructed with its creators and remains shrouded in mystery. The first theory points to the Chapin family's history as soldiers. The Chapin family's founder Deacon Samuel Chapin was one of the early settlers of the Massachusetts Bay Colony in the early 1630s. His bloodline continued throughout American history, including connections to President Grover Cleveland and William H. Taft, abolitionist Henry Ward Beecher, and Poet T.S. Eliot. The Chapin family also had several famous soldiers and war leaders, including General Israel Chapin. It is thought the name Northern Spy apples was taken from an 1821 book written by James Fennimore Cooper entitled The Spy: A Tale of the Neutral Ground. The novel's plot involves a man spying on the British during the Revolutionary War. Legend has it the book was inspired by John Jay, a revolutionary who helped form the U.S. counterintelligence. John Jay was a friend and colleague of General Israel Chapin, thus tying together the theory that Northern Spy may have been derived from the Chapin family's involvement and close relations to various members of secret intelligence. The other leading theory connects the apple's name to a written piece that was circulated among abolitionists in the 1830s. This piece told the story of a "Northern Spy" who established safehouses to transport slaves from Virginia to New York. The spy would impersonate a slave catcher and would usher slaves to safety, killing leaders in the pro-slavery movement. Much of the history of this written piece is unknown, but it was said to have later inspired the book written by J. Thomas Warren called The Northern Spy: The Fatal Papers.