Williams Haynes was born in Detroit, where his father, David Oliphant Haynes, was the publisher of The Pharmaceutical Era, as well as the president and the general manager of D. O. Haynes & Co. In 1896 D. O. Haynes established in New York City the New York Commercial as a daily newspaper on business.
Williams Haynes worked as a reporter for the New York Sun and as an editor for Field and Fancy from 1906 to 1907. He enrolled in 1908 as a special student at Johns Hopkins University, where he studied economics, biology, and chemistry, but left in 1911 without a degree. He married his first wife in June 1911. From 1911 to 1916 he was a contributor to magazines and newspapers and at various times visited Canada and Europe as a journalist. From 1914 to 1915 he was editor-in-chief of the Northampton, Massachusetts Herald (a daily newspaper). In 1916 he became the editorial director of D. O. Haynes & Co. As editorial director he was responsible for the chemical industry journal Drug and Chemical Markets and in 1920 became the journals publisher. In 1926 he split the journal into two journals: Drugs and Cosmetics Industry and Chemical Industries (later called Chemical Week under the ownership of McGraw-Hill). In 1926 he also began publishing Plastic Products (renamed Modern Plastics, published from 1934 to 2004). In 1928 he established the book series Chemical Who’s Who' and was editor-in-chief of the series until 1951. In 1939 Haynes sold his interest in the trade journals in order to focus his efforts as an author and editor. He moved to a property near Stonington in eastern Connecticut. The property, which had been in his family for several generations, had a farmhouse built in 1750.
As a journalist he contributed to The Outlook, The Nation, The Dial, Science, and Outing, among other publications. His extensive photo collection of chemists came to the Science History Institute through The Chemists' Club of New York.
In 1950 Haynes was awarded the Honorable Cornelius Amory Pugsley Bronze Medal for his work in protecting the natural environment. In 1957 he received the Dexter Award for his work as a historian of the American chemical industry.
He was married twice. There were two daughters from his second marriage.