He moved to Paris about 1872 and studied at the École des Beaux-Arts for a year where Renaissance art influenced his ideas of design. He returned to Chicago, wishing to emulate Michelangelo's creations and by 1880, Sullivan became a partner in the firm of Adler and Sullivan.
Adler and Sullivan achieved wide fame, but an economic downturn in 1893 spelled doom for the firm of Adler and Sullivan. Adler left the firm and once again, Louis Sullivan was alone and he did not do well. The Carson Pririe Scott & Co. department store was his last large commission.
In the twilight of his career, Sullivan designed several small office buildings and a department store in Clinton, Iowa.
But his farewell gift to architecture was comprised of eight bank buildings commissioned from around the Midwest. He dubbed the designs "Jewel Boxes" for their simple but strong external appearance, with the security shown for the gems locked firmly inside.
When asked why the bank should buy his design, far more expensive than other architect's building designs, Sullivan replied, "A thousand architects could design those buildings. Only I can design this one."
These eight Jewel Boxes still exist and some still house banking operations. Sullivan once said "It is the pervading law…that form always follows function. This is the law." The fact that his 100 year old bank designs still function as banks proves his point - form always follows function.