Start of her career After completing her degree at MIT, Mahony returned to Chicago and started her professional career at her cousin, Dwight Perkins' practice in Chicago’s
Steinway Hall, a shared office of more progressive artists and architects during the time. Perkins himself was a former MIT student, however he never completed his architectural degree. Although Mahony was more educated than him, he fostered the significant improvement of her drafting and design skills as she gained hands-on experience. Subsequently, she became the first licensed female architect in Illinois in 1898. She was later hired and worked with Wright from 1895–1909 in both Chicago and his Oak Park studio. She went to work designing buildings, furniture,
stained glass windows, and decorative panels.
Barry Byrne, a coworker of Mahony's described her as “the most talented member of Frank Lloyd Wright’s staff." She combined art and architecture in her draftsmanship, and was known to have an "exceptional feel" for linear compositions that integrated architecture with nature. Her interest in Japanese prints gave her several unique compositional techniques of color, depth, emphasis, and line weight that played a crucial role in the development of the Prairie School. This new presentation of designs was revolutionary in presenting architectural work to the world. Mahony's work became a powerful marketing tool, that enabled conversations with clients as they had become able to visualize the plans presented. Her rendering of the
K. C. DeRhodes House in
South Bend, Indiana, in particular, was praised by Wright and many critics. Her presentation drawing of the home was exceptionally skillful with clear-cut lines, and her original use of stylized trees and flowers to frame the structure. The foliage was just as sharp as the structure presented, further highlighting her integration of architecture with the natural world. Her watercolor renderings of buildings and landscapes became known as a staple of Wright's style, though she was never given credit by the famous architect. For example, Wright "desperately" tried to attribute the
K. C. DeRhodes House to himself. He annotated the rendering writing "after FLLW and Hiroshige". Yet, Mahony's initials, "MLM", were included in very small print under the foliage of the rendering. After Wright had gone,
Hermann V. von Holst, who had taken on Wright's commissions, hired Mahony with the stipulation that she would have control of the design. in
Grand Rapids, Michigan. During this time, Mahony recommended
Walter Burley Griffin to von Holst to develop landscaping for the area surrounding the three houses commissioned from Wright in
Decatur, Illinois. Griffin was a fellow architect, a fellow ex-employee of Wright, and a leading member of the
Prairie School of architecture. Mahony and Griffin worked on the Decatur project before their marriage in 1911; afterward, Mahony worked in Griffin's practice. However, deeply rooted in her collaborative approach, she would publicly refer to her contributions as "our projects", often making note of the love and loyalty she had for her husband. Cafe Australia,
Newman College, and the
Capitol Theatre were three architectural structures worked on by Mahony, and for which the couple hired local artists, Marion's memoirs record the rough journey across
Bass Strait in the
SS Loongana, compensated over December 1918–January 1919 with 'a wonderful fortnight which enabled me to add a number of unique trees to my set of Forest Portraits.' In Australia, Mahony and Griffin was introduced to
Anthroposophy and the ideas of
Rudolf Steiner which they embraced enthusiastically, and in
Sydney they joined the Anthroposophy Society. These would later have a great influence on her autobiography. In a manuscript of the letter between the two included in "The Magic of America", Mr. Halder stated, "Marion is working like a slave and she is the only effective help I have had for this exhibition." In addition to this, she continued drafting and illustrating in her unique graphic style, yet it's hard to attribute which of her works belonged to her when both she and her husband signed their initials on them. Lucknow reinvigorated her interest in architecture as she finished the rendering of the library and museum for
Raja of Mahmudabad as Walter Burley Griffin lay on his death bed. Her artistic approach in this piece was deemed to be an evolution of the renderings she had produced earlier. It was not only an expression of the building, but a work of graphic art that shared characteristics with the rendering of the DeRhodes house. ==Death and legacy==