Ahead of his time and sensing opportunities across the Atlantic, Nathan opened a gallery in New York in 1903, followed by another in London in 1925. Seizing on the importance of educating the new generation of Industrialists and railroad magnates, Nathan's careful and informed cultural tutelage of the likes of Jules S. Bache, Henry Ford, Edward G. Robinson, the Havermeyers, Henry and Arabella Huntington and Mortimer Schiff ultimately provided the backbones of the great bequests to American Museums. The business he created in the 1870s, grew into a vast enterprise that today includes galleries in New York and Tokyo and a research institute in Paris.

From before the turn of the century to the end of his life, Nathan Wildenstein began a collection which was housed in his principal home in Paris at 57, rue de la Boétie which he had acquired in 1905 following the continued success of the business. The building had been designed in 1776 by Charles de Wailly, one of the two architects of the Théâtre de l'Odéon, for his own use.

Nathan gave the building its present configuration with the succession of sitting rooms and galleries designed to showcase works of art and house a library. Many of the pieces he acquired were from some of the most prestigious collections including the French Rothschilds, Doucet, David-Weil, Kann, Lion, Burat, Bensimon, Helft, Seligmann, Lévy, Kraemer and Veil-Picard.

While a few of the pieces were illustrated in Charles Packer's Paris Furniture published in 1956, the majority are little known, even in illustrations.

Nathan's son, Georges Wildenstein (1892-1963) inherited his father's eye and instincts and also cultivated a broader interest in the academic pursuit of art history itself. He assembled an extraordinary library and photographic archive, concentrating particularly on the late 19th century, and purchased works by Cézanne, Degas, Manet and Monet. Georges' passion for French art and culture knew no bounds, and his profound understanding of them was conditioned not only by his reading and the elaborate research projects he initiated, but also by his visits to art museums, exhibitions, commercial galleries, auction houses and homes of private collectors.