On May 20, 1818, William married Margaret Alida Rebecca Armstrong (1800–1872), the daughter of Senator
John Armstrong Jr. and Alida (
née Livingston) Armstrong and sister of
Horatio Gates Armstrong. Her mother, a member of the prominent
Livingston family, was the youngest child of
Judge Robert Livingston and Margaret (née Beekman) Livingston as well as the sister of
Chancellor Robert R. Livingston and
Secretary of State Edward Livingston. Her father, John Armstrong Jr. was President
James Madison's second Secretary of War. Together, William and Margaret had seven children: a financier/lobbyist/author, on January 5, 1838, and had two children. •
John Jacob Astor III (1822–1890), on December 9, 1846, and had one son. • Mary Alida Astor (1823–1881), who married John Carey (1821–1881) on April 16, 1850, and had three children. • Laura Eugenia Astor (1824–1902), who married
Franklin Hughes Delano (1813–1893), on September 17, 1844 (no issue). •
William Backhouse Astor Jr. (1829–1892), who married socialite
Caroline Webster "Lina" Schermerhorn (1830–1908) on September 20, 1853, and had five children. • Henry Astor III (1830–1918), who married Malvina Dinehart (1844–1918) in 1871 after which he was estranged from his family (no issue). • Sarah Todd Astor (1832–1832), who died in infancy. As a wedding gift, Astor gave Franklin and Laura Delano the southernmost 100 acres of
Rokeby estate. The estate came to be known as "Steen Valetje" (which means "little stone valley" in Dutch). Margaret Astor died on February 15, 1872. William Astor survived his wife by three years, dying on November 24, 1875, in his townhouse at
Lafayette Place in
New York City. He was buried next to his wife in the Astor vault at
Trinity Church Cemetery, designed by
Frederick Clarke Withers, in New York City. In 1866, he conveyed the adjoining 142 acres of Rokeby to his son, Henry, who built a brick dwelling on this land, but in 1873, conveyed the property to Laura. Astor's local newspaper
The New York Times eulogised, Mr. William B. Astor. 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. Mr. Astor was in his usual good health, except for a slight cold, until Saturday of last week. On that morning his cold began to trouble him and occasioned a severe cough. ==See also==