[1] His seven siblings were Magdalena (1788–1832), Sarah (1790–1790), John Jr. (1791–1869), Dorothea (1795–1874), Henry (1797–1799), Eliza (1801–1838), and an unnamed brother who died shortly after his November 13, 1802, birth.

[5] In 1815, he returned to the United States and entered partnership with his father, who changed the name of his firm to John Jacob Astor & Son and engaged in the China trade.

[5] William's elder brother John Jacob Astor Jr. was sickly and mentally unstable, and had no part in the business.

[6] Although William's fortunes grew with his father's company, he became a truly wealthy man when he inherited the estate, worth around $500,000 (equivalent to roughly $507 million in 2024[7]), of his childless uncle Henry Astor I, who died in 1833.

[10] During the American Civil War he successfully brought a case against the income tax imposed by the United States government, which was ruled unconstitutional.

[14] Together, William and Margaret had seven children:[15] As a wedding gift, Astor gave Franklin and Laura Delano the southernmost 100 acres of Rokeby estate.

[15] He was buried next to his wife in the Astor vault at Trinity Church Cemetery, designed by Frederick Clarke Withers, in New York City.

an illness of four days ends an honored and successful life the public events in Mr. Astor's career a ripe scholar and philanthropic man.

Mr William B. Astor, after an illness of only a few days, died at his residence in this City yesterday at 9:30 A.M., aged eighty three years.