architect, one of the greatest practitioners in the Chicago School of commercial American architecture. His works are among the most distinguished early attempts at a mature aesthetic expression of the height and the function of the skyscraper.

Sent to England for safety during the American Civil War (1861–65), Root attended Oxford for a year. Having returned to the United States in 1866, he received a degree in civil engineering from New York University in 1869. After two years (1871–73) as head draftsman for the Chicago architectural firm of Carter, Drake, and Wight, he joined another draftsman, Daniel H. Burnham (Burnham, Daniel H.), in a partnership that became one of the most famous firms in U.S. architectural history. Burnham and Root's first important commercial building was the Montauk Building (1882; demolished 1902). To meet the problem of supporting this 10-story structure on masonry footings (piers) in the soft Chicago soil, Root incorporated into the foundation a grillage of iron rails, thereby distributing the weight over the entire ground area. Another major technical innovation in the Montauk Building was the use of flat tile arches in the floors for fireproofing.

Root died of pneumonia while serving on the architectural staff of the World's Columbian Exposition, Chicago. He wrote many papers on the philosophy of the new architectural movement in Chicago.