Around 1900 a number of architects around the world began developing new architectural solutions to integrate traditional precedents with new social demands and technological possibilities. The work of Victor Horta and Henry van de Velde in Brussels, Antoni Gaudí in Barcelona, Otto Wagner in Vienna and Charles Rennie Mackintosh in Glasgow, among many others, can be seen as a common struggle between old and new. These architects were not considered part of the International Style because they practiced in an "individualistic manner" and seen as the last representatives of Romanticism.
The International Style can be traced to buildings designed by a small group of modernists, of which the major figures includes Ludwig Mies van der Rohe, Jacobus Oud, Le Corbusier, Richard Neutra and Philip Johnson.
The founder of the Bauhaus school, Walter Gropius, along with prominent Bauhaus instructor, Ludwig Mies van der Rohe, became known for steel frame structures employing glass curtain walls. One of the world's earliest modern buildings where this can be seen is a shoe factory designed by Gropius in 1911 in Alfeld-an-der-Leine, Germay, called the Fagus Works building. The first building built entirely on Bauhaus design principles was the concrete and steel Haus am Horn, built in 1923 in Weimar, Germany, designed by Georg Muche. The Gropius designed Bauhaus school building in Dessau, built 1925–26 and the Harvard Graduate Center (Cambridge, Massachusetts; 1949–50) also known as the Gropius Complex, exhibit clean lines and a "concern for uncluttered interior spaces".
Marcel Breuer, a recognized leader in Béton Brut (Brutalist) architecture and notable alumni of the Bauhaus, who also pioneered the use of plywood and tubular steel in furniture design, and who after leaving the Bauhaus would later teach alongside Gropius at Harvard, is as well an important contributor to Modernism and the International Style.
Prior to use of the term 'International Style', some American architects—such as Louis Sullivan, Frank Lloyd Wright, and Irving Gill—exemplified qualities of simplification, honesty and clarity.
Frank Lloyd Wright's Wasmuth Portfolio had been exhibited in Europe and influenced the work of European modernists, and his travels there probably influenced his own work, although he refused to be categorized with them. His buildings of the 1920s and 1930s clearly showed a change in the style of the architect, but in a different direction than the International Style.
In Europe the modern movement in architecture had been called Functionalism or Neue Sachlichkeit (New Objectivity), L'Esprit Nouveau, or simply Modernism and was very much concerned with the coming together of a new architectural form and social reform, creating a more open and transparent society.
The "International Style", as defined by Hitchcock and Johnson, had developed in 1920s Western Europe, shaped by the activities of the Dutch De Stijl movement, Le Corbusier, and the Deutscher Werkbund and the Bauhaus. Le Corbusier had embraced Taylorist and Fordist strategies adopted from American industrial models in order to reorganize society. He contributed to a new journal called L'Esprit Nouveau that advocated the use of modern industrial techniques and strategies to create a higher standard of living on all socio-economic levels. In 1927, one of the first and most defining manifestations of the International Style was the Weissenhof Estate in Stuttgart, overseen by Ludwig Mies van der Rohe. It was enormously popular, with thousands of daily visitors.