Frank Lloyd Wright in the context of "Urbanists"

Louis Henry Sullivan (September 3, 1856 – April 14, 1924) was an American architect, and has been called a "father of skyscrapers" and "father of modernism". He was an influential architect of the Chicago School, a mentor to Frank Lloyd Wright, and an inspiration to the Chicago group of architects who have come to be known as the Prairie School. Along with Wright and Henry Hobson Richardson, Sullivan is one of "the recognized trinity of American architecture." The phrase "form follows function" is attributed to him; it encapsulated earlier theories of architecture and he applied them to the modern age of the skyscraper. In 1944, Sullivan was the second architect to posthumously receive the AIA Gold Medal.

Eugène Emmanuel Viollet-le-Duc (French: [øʒɛn vjɔlɛ lə dyk]; 27 January 1814 – 17 September 1879) was a French architect and author, famous for his restoration of the most prominent medieval landmarks in France. His major restoration projects included Notre-Dame de Paris, the Basilica of Saint Denis, Mont Saint-Michel, Sainte-Chapelle, the medieval walls of the city of Carcassonne, and Château de Roquetaillade in the Bordeaux region.

His writings on decoration and on the relationship between form and function in architecture had a fundamental influence on a whole new generation of architects, including all the major Art Nouveau artists: Antoni Gaudí, Victor Horta, Hector Guimard, Henry van de Velde, Henri Sauvage and the École de Nancy, Paul Hankar, Otto Wagner, Eugène Grasset, Émile Gallé, and Hendrik Petrus Berlage. He also influenced the first modern architects, Frank Lloyd Wright, Mies van der Rohe, Auguste Perret, Louis Sullivan, and Le Corbusier, who considered Viollet-le-Duc as the father of modern architecture. English architect William Burges claimed that "We all cribbed on Viollet-le-Duc even though no one could read French".

Prairie School is a late 19th and early 20th-century architectural style, most common in the Midwestern United States. The style is usually marked by horizontal lines, flat or hipped roofs with broad overhanging eaves, windows grouped in horizontal bands, integration with the landscape, and solid construction and craftsmanship. It reflects discipline in the use of ornament, which was often inspired by organic growth and seen carved into wood, stenciled on plaster, in colored glass, veined marble, and prints or paintings with a general prevalence of earthy, autumnal colors. Spaciousness and continuous horizontal lines were thought to evoke and relate to the wide, flat, treeless expanses of America's native prairie landscape, and decoration often depicted prairie wildlife, sometimes with indigenous materials contributing to a sense of the building belonging to the landscape.

The Prairie School sought to develop an indigenous North American style of architecture, distinguishing it from historical revivals that were popular at the time. It shared many ideals and design aesthetics of the Arts and Crafts Movement, though it embraced the machine and also shared ideals with modernist movements. Many architects were also part of the Chicago School, but Prairie School buildings were seen less in the commercial skyscrapers of Chicago and more in the suburban residences, though the style can be seen in throughout a variety of building types, including banks, schools, and churches. Japanese architecture and prints, interests of Frank Lloyd Wright in particular, inspired the focus on simplicity and openness in addition to the prairie landscape.

Henry Hobson Richardson, FAIA (September 29, 1838 – April 27, 1886) was an American architect, best known for his work in a style derived from Romanesque Revival that became known as Richardsonian Romanesque. Along with Louis Sullivan and Frank Lloyd Wright, Richardson is one of "the recognized trinity of American architecture."

The Wainwright Building (also known as the Wainwright State Office Building) is a 10-story, 41 m (135 ft) terra cotta office building at 709 Chestnut Street in downtown St. Louis, Missouri. The Wainwright Building is considered to be one of the first aesthetically fully expressed early skyscrapers. It was designed by Dankmar Adler and Louis Sullivan and built between 1890 and 1891. It was named for local brewer, building contractor, and financier Ellis Wainwright.

The building, listed as a landmark both locally and nationally, is described as "a highly influential prototype of the modern office building" by the National Register of Historic Places. Architect Frank Lloyd Wright called the Wainwright Building "the very first human expression of a tall steel office-building as Architecture."

McKim, Mead & White was an American architectural firm based in New York City. The firm came to define architectural practice, urbanism, and the ideals of the American Renaissance in fin de siècle New York.

The firm's founding partners, Charles Follen McKim (1847–1909), William Rutherford Mead (1846–1928), and Stanford White (1853–1906), were giants in the architecture of their time, and remain important as innovators and leaders in the development of modern architecture worldwide. They formed a school of classically trained, technologically skilled designers who practiced well into the mid-20th century. According to Robert A. M. Stern, only Frank Lloyd Wright was more important to the identity and character of modern American architecture.

Frank Lloyd Wright designed 1,141 houses, commercial buildings and other works throughout his lifetime, including 532 that were eventually built. As of 2013, there were 409 extant structures designed by Wright. Over one-third of the extant structures are on the U.S. National Register of Historic Places, either as part of their own designation or as part of a historic district. UNESCO added eight of Wright's designs to the World Heritage List in July 2019 under the title "The 20th-Century Architecture of Frank Lloyd Wright".