In 1913, Mies married Adele Auguste (Ada) Bruhn (1885–1951), the daughter of a wealthy industrialist. The couple separated in 1918, after having three daughters: Dorothea (1914–2008), an actress and dancer who was known as Georgia, Marianne (1915–2003), and Waltraut (1917–1959), who was a research scholar and curator at the Art Institute of Chicago. During his military service in 1917, Mies fathered a son out of wedlock.

While continuing his traditional neoclassical design practice, Mies began to develop visionary projects that, though mostly unbuilt, rocketed him to fame as an architect capable of giving form that was in harmony with the spirit of the emerging modern society. Boldly abandoning ornament altogether, Mies made a dramatic modernist debut in 1921 with his stunning competition proposal for the faceted all-glass Friedrichstraße skyscraper, followed by a taller curved version in 1922 named the Glass Skyscraper.

He joined the German avant-garde, working with the progressive design magazine G, which started in July 1923. He developed prominence as architectural director of the Werkbund, organizing the influential Weissenhof Estate prototype modernist housing exhibition. He was also one of the founders of the architectural association Der Ring. He joined the avant-garde Bauhaus design school as their director of architecture, adopting and developing their functionalist application of simple geometric forms in the design of useful objects. He served as its last director.

In 1925 Mies began a relationship with designer Lilly Reich that ended when he moved to the United States; from 1940 until his death, artist Lora Marx (1900–1989) was his primary companion. Mies carried on a romantic relationship with sculptor and art collector Mary Callery for whom he designed an artist’s studio in Huntington, Long Island, New York. He also was rumored to have a brief relationship with Edith Farnsworth, who commissioned his work for the Farnsworth House. His daughter Marianne’s son, Dirk Lohan (b. 1938), studied under, and later worked for, Mies.

He constructed his first modernist house with the Villa Wolf in 1926 in Gubin, in today’s Poland, for Erich and Elisabeth Wolf. This was shortly followed by Haus Lange and Haus Esters in 1928.

He continued with a series of pioneering projects, culminating in his two European masterworks: the temporary German Pavilion for the Barcelona exposition (often called the Barcelona Pavilion) in 1929 (a 1986 reconstruction is now built on the original site) and the elegant Villa Tugendhat in Brno, Moravia, Czechia, completed in 1930.

Commission opportunities dwindled with the Great Depression after 1929. Starting in 1930, Mies served as the last director of the faltering Bauhaus, at the request of his colleague and competitor Walter Gropius. In 1932, Nazi political pressure forced the state-supported school to leave its campus in Dessau, and Mies moved it to an abandoned telephone factory in Berlin. By 1933, however, the continued operation of the school was untenable (it was raided by the Gestapo in April), and in July of that year, Mies and the faculty voted to close the Bauhaus. He built very little in these years (one built commission was Philip Johnson’s New York apartment); the Nazis rejected his style as not “German” in character.

Frustrated and unhappy, he left his homeland reluctantly in 1937 as he saw his opportunity for any future building commissions vanish, accepting a residential commission in Wyoming and then an offer to head the department of architecture of the newly established Illinois Institute of Technology (IIT) in Chicago. There he introduced a new kind of education and attitude later known as Second Chicago School, which became very influential in the following decades in North America and Europe.

In 1944, he became an American citizen, completing his severance from his native Germany. His thirty years as an American architect reflect a more structural, pure approach toward achieving his goal of a new architecture for the twentieth century. He focused his efforts on enclosing open and adaptable “universal” spaces with clearly arranged structural frameworks, featuring prefabricated steel shapes filled in with large sheets of glass.

Between 1946 and 1951, Mies van der Rohe designed and built the Farnsworth House, a weekend retreat outside Chicago for an independent professional woman, Dr. Edith Farnsworth. Here, Mies explored the relationship between people, shelter, and nature. The glass pavilion is raised six feet above a floodplain next to the Fox River, surrounded by forest and rural prairies.

Mies designed two buildings for the Museum of Fine Arts, Houston (MFAH) as additions to the Caroline Wiess Law Building. In 1953, the MFAH commissioned Mies van der Rohe to create a master plan for the institution. He designed two additions to the building—Cullinan Hall, completed in 1958, and the Brown Pavilion, completed in 1974. A renowned example of the International Style, these portions of the Caroline Wiess Law Building comprise one of only two Mies-designed museums in the world.

The One Charles Center, built in 1962, is a 23-story aluminum and glass building that heralded the beginning of Baltimore’s downtown modern buildings. The Highfield House, just to the northeast of the Johns Hopkins Homewood campus, was built in 1964 as a rental apartment building. The 15-story concrete tower became a residential condominium building in 1979. Both buildings are now on the National Register of Historic Places.

Over the last twenty years of his life, Mies developed and built his vision of a monumental “skin and bones” architecture that reflected his goal to provide the individual a place to fulfill himself in the modern era. Mies sought to create free and open spaces, enclosed within a structural order with minimal presence. In 1963, he was awarded the Presidential Medal of Freedom.

The Ludwig Mies van der Rohe Archive, an administratively independent section of the Museum of Modern Art’s department of architecture and design, was established in 1968 by the museum’s trustees. It was founded in response to the architect’s desire to bequeath his entire work to the museum. The archive consists of about nineteen thousand drawings and prints, one thousand of which are by the designer and architect Lilly Reich (1885–1947), Mies van der Rohe’s close collaborator from 1927 to 1937; of written documents (primarily, the business correspondence) covering nearly the entire career of the architect; of photographs of buildings, models, and furniture; and of audiotapes, books, and periodicals.

Mies’s grandson Dirk Lohan and two partners led the firm after he died in 1969. Lohan, who had collaborated with Mies on the New National Gallery, continued with existing projects but soon led the firm on his own independent path. Other disciples continued Mies’s architectural language for years, notably Gene Summers, David Haid, Myron Goldsmith, Y.C. Wong, Jacques Brownson, and other architects at the firms of C.F. Murphy and Skidmore, Owings & Merrill.

Mies van der Rohe died on August 17, 1969, from esophageal cancer caused by his smoking habit. After cremation, his ashes were buried near Chicago’s other famous architects in Chicago’s Graceland Cemetery. His grave is marked by a simple black slab of granite and a large honey locust tree.

The Farnsworth House and its 60-acre (240,000 m) wooded site was purchased at auction for US$7.5 million by preservation groups in 2004 and is now owned and operated by the National Trust for Historic Preservation as a public museum. The building influenced the creation of hundreds of modernist glass houses, most notably the Glass House by Philip Johnson, located near New York City and also now owned by the National Trust.