[1] Hamilton McKown Twombly Sr. was born on August 11, 1849, in Middlesex County, Massachusetts, and grew up in Boston.

[1] Twombly worked as a financial advisor to William Henry Vanderbilt (1821–1885), President of the New York Central Railroad.

[1] In 1890, Abram Hewitt partnered with Edward Cooper and Hamilton M. Twombly in forming the American Sulphur Company.

That company then entered into a 50/50 agreement with Herman Frasch and his partners to form the Union Sulphur Company[3] In 1892, Twombly and his wife were both included in Ward McAllister's "Four Hundred", purported to be an index of New York's best families led by Mrs. Astor, as published in The New York Times.

[20][21] His funeral took place at Saint Thomas Church in New York, with a sermon by David H. Greer (1844–1919), and the banker J. P. Morgan (1837–1913) was one of the pallbearers.