[1] When Atlanta fell to the Union during the American Civil War, Root's father sent young Root and one other boy on a steamer to the United Kingdom,[2] where his father, Sidney, had a shipping business based in Liverpool, England.

[3] His later design work was said to have been influenced by the pioneering work of Liverpool architect Peter Ellis, who designed and built the world's first two metal-framed, glass curtain-walled buildings, Oriel Chambers (1864) and 16 Cook Street (1866).

[5] During the economic downturn in 1873, Root earned extra income on jobs with other firms and as the organist at the First Presbyterian Church.

Root developed the floating raft system of interlaced steel beams, to create a foundation for tall buildings that would not sink in Chicago's marshy soil.

[5] Root married Mary Louise Walker in 1879, but she died of tuberculosis six weeks later.

Their son John Wellborn Root Jr. also practiced in Chicago as an architect.