William Henry Breithaupt was born in Buffalo, New York January 25, 1857 to parents Philip Louis (Ludwig) and Catherine Hailer. His siblings were Louis Jacob; John Christian; Caroline Margaret; Melvina Emilia; Ezra Carl; Daniel Edward; Albert Liborius; Catharine Louise and Friederick Adolph. The family moved to Berlin (later Kitchener) Ontario in 1861.

William attended Berlin Collegiate Institute in Kitchener, Ontario, Commercial School in Toronto and then North Western College, Naperville, Illinois. He entered Rensselaer Polytechnic Institute of Troy, New York in September of 1877. He worked in construction on the New York, West Shore and Buffalo railroad August 1881, working mainly on the West Point tunnel. in January 1883 he was appointed bridge inspector for the Pennsylvania railroad company and in October of the same year assistant engineer for C. Shaler Smith of St. Louis, Missouri. In 1886 he had his own company Breithaupt & Allen, civil engineer based in Kansas City, Missouri.

William married Martha Cunningham Murphy February 1, 1898 in Montreal, Quebec. The couple had three children: Philip W,; Margaret Catharine and Martha Elizabeth. In 1907 William was in a partnership with E.H. Keating in Toronto, Ontario. The couple moved to Berlin, Ontario. William was an entrepreneur and professional engineer, and his diaries contain notes on town planning in Kitchener, environmental protection of the Grand River watershed and early local public works projects such as public transportation, the Berlin and Waterloo Railway, the Bridgeport Line, and also water and power supplies. The history of the Berlin Gas Works is documented in the diaries and also in correspondence with his brother, Ezra Carl, also an engineer, who died in 1897 in an explosion at the gas works. William also served as President of the Waterloo Historical Society.

William died January 27, 1944 due to complications from a fall at home, and is buried in Mount Hope Cemetery, Kitchener. His wife, Martha died in 1950 and is buried with William.

The Wagners and Hailers were prominent early settler families in Waterloo County, Ontario, as were the Staebler, Biehn/Bean and Breithaupt families.