There was money in the air, ever so much money, wrote Henry James in 1907, reflecting on the American appetite for art acquisitions. Indeed, collectors such as Henry Clay Frick and Andrew W. Mellon are credited with bringing noteworthy European art to the United States, with their collections forming the backbone of major American museums today. But what of the dealers, who possessed the expertise in art and recognized the potential of developing a new market model on both sides of the Atlantic? Money in the Air investigates the often-overlooked role of these dealers in creating an international art world. Contributors examine the histories of well-known international firms like Duveen Brothers, M. Knoedler & Co., and Goupil Cie and their relationships with American clients, as well as accounts of other remarkable dealers active in the transatlantic art market. Drawing on dealer archives, scholars reveal compelling findings, including previously unknown partnerships and systems of cooperation. This volume offers new perspectives on the development of art collections that formed the core of American art museums, such as the National Gallery of Art, the Metropolitan Museum of Art, and the Frick Collection.