Mackintosh often designed rooms down to the last detail. His holistic approach to design included the use of symbols and stylized Celtic elements as well as the balancing of opposites; modernity with tradition, light with dark, the masculine with the feminine. In 1914, he left Glasgow and moved to London, where his work included designs for rhythmically patterned textiles and furniture with strong graphic lines.

Mackintosh designed several public buildings and private residences in Glasgow at the turn of the century, including his masterwork, the Glasgow School of Art (1896-1909). Hill House, Miss Cranston's tea rooms and his own house in Glasgow are examples of a unique genius that did not mimic the predominant Art Nouveau style but created its own world of color, pattern and form. Mackintosh's elliptical high-backed chairs adorned the Argyle Street tea rooms and his later rooms in Ingram Street and Willow Street are integrated works of art designed by him down to the cutlery.

Unable to secure architectural commissions in London, he moved to Port Vendres, in the South of France where he devoted himself to painting watercolors. Although clients seemed to desert him in later life, Mackintosh was the leading designer of the Glasgow School and his influence was considerable. The high-backed chair with its dramatically elongated backrest is among the most famous pieces, its unusual proportions never failing to arrest the eye.