William B. Coster

Coster was born in New York and lived at a large home at 103 East 71st Street. He was one of four children born to Charles Robert Coster (1839–1888)[2][3] and Marie Bay (née James) Coster (1841–1904),[4][5] who were married in 1864.[6] Among his siblings was brother Charles Coster,[lower-alpha 1][9] and sister Elizabeth Mary Coster, who married Alfred Egmont Schermerhorn.[lower-alpha 2][10] His father was a soldier and public official, who is best known for commanding a brigade at the Battle of Gettysburg.[13]

His maternal grandfather was Augustus J. James of Albany, the brother of theologian Henry James Sr.,[10] making William's mother Marie a first cousin of author Henry James, psychologist William James, and diarist Alice James.[14] His paternal grandparents were John H. Coster and Sarah Adeline (née Boardman) Coster,[15] making his father a first cousin of fellow New York clubman, Harry Coster.[16][lower-alpha 3] His great-grandfather, John Gerard Coster,[18] came from Haarlem in the Netherlands to the United States shortly after the Revolutionary War and founded the family fortune through the mercantile firm, "Henry A. & John G. Coster".[19]

Coster became a stockbroker and opened up an office with his brother Charles and John M. Knapp in 1893.[20] He later transferred his seat to Knapp in 1907, and resigned from the firm.[21] He later became a partner in Morgan Drexel.[22] He was known as a speed walker, who could be seen "traversing the sidewalks between the New York Athletic Club and the stock exchange in record time."[20]

In 1908, his brother committed suicide "after he'd been caught bilking his customers out of millions of dollars."[20][21] Although William was accused of wrongdoing, and, along with his other siblings, worked out of the same office as Charles,[7] William himself was eventually declared by the New York Stock Exchange to be completely innocent in the debacle.[20][23]

Coster also served in the New York National Guard as the aide de camp of the First Brigade, achieving the rank of captain in 1896.[24][25]

On October 1, 1900,[28] Coster was married to Maria "Minnie" Griswold Gray (1868–1947)[29] at St. Saviour's Episcopal Church in Bar Harbor, Maine.[30] Minnie, a close friend of etiquette author Emily Post,[20] was the daughter of Henry Winthrop Gray[31] and Mary (née Travers) Gray, and the granddaughter of William R. Travers.[lower-alpha 4] Her parents divorced and her father remarried to Matilda Frelinghuyhsen (daughter of U.S. Secretary of State F. T. Frelinghuysen[33]) in May 1889.[34] Together, William and Maria first lived in New York, then Paris,[35] and became the parents of three children:[36]

• Matilda Gray Coster (1901–1962),[36] who married Stanley Yates Mortimer Jr. (1897–1984), a grandson of Valentine Hall Jr., nephew of Richard Mortimer, and first cousin of Eleanor Roosevelt, in 1925.[37] They divorced in 1928,[38] and she remarried to Luis Martínez de las Rivas, in 1932.[39] They later lived in Cuernavaca, Mexico.[29]
• Mary Griswold Coster (1903–1918),[36] who died of pneumonia at age 15.[40]
• William Bay Coster Jr. (1908–1945), who rowed on the Pembroke College crew at Oxford and was an air-raid warden in London during World War II.[36]

After living in New York and Paris for many years, Coster died "of a long illness, patiently borne," in Bournemouth, England on December 19, 1918.[1] His widow, who lived in Paris at 5 Rue Vaneau, died at her home, 39 East 79th Street in New York, at the age of 79 in July 1947.[41]

Notes

Sources

• Photograph of Coster's granddaughter, Mathilda Coster Campbell, Duchess of Argyll, by Madame Yevonde, mid 1960s, at the National Portrait Gallery.