William Bay Coster (1867 – December 19, 1918)[1] was an American banker who was prominent in New York Society during the Gilded Age.
[16][c] 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.
[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][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.
[22] 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.
[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.