Born Jean Babtiste Coupa in 1808, John Coupa was a successful guitarist and instructor who began selling guitars by C.F. Martin as early as 1837 from his studio at 385 Broadway in Lower Manhattan. When Martin relocated to Cherry Hill, Pennsylvania in 1839, Coupa became Martin’s primary sales representative in New York City, marketing guitars under the Martin & Coupa label. Throughout the 1840s until his death in 1850, Coupa’s input influenced Martin’s transition away from the Stauffer-style guitars of the Viennese School to the work of the Spanish makers of Cadíz. Shallow bodies, symmetrical bouts, ladder braces, and pin bridges gave way to deeper bodies, rectangular tie bridges, fan braces, and greater differentiation in the sizes of the upper and lower bouts. Peg and slotted heads slowly replaced the signature scroll-shaped design typical of Martin’s Stauffer-school pedigree. Coupa’s endorsement during the transformational decade of the 1840s secures his place as a pivotal figure in Martin guitar history.