Wainwright was born on August 3, 1850, and although the family hailed from Godfrey, Illinois, he grew up in nearby St. Louis, where he also spent much of his adult life.

[1][3] The son of a prominent brewer and building contractor, an English immigrant named Samuel and Catherine Dorothy, Wainwright was an important figure in railway development in the region.

[8] Architect Frank Lloyd Wright called the Wainwright Building "the very first human expression of a tall steel office-building as Architecture.

In 1902, Wainwright was indicted for conspiracy to bribe members of the state legislature in the Suburban Railway boodle scandal and subsequently became a fugitive in Paris.

[4] In 1904, his name appeared in The Shame of the Cities, a muckraking exposé by Lincoln Steffens which gave details of Wainwright's shady dealings and other public corruption within the United States.