William Lewis Dayton Jr. (April 13, 1839 – July 28, 1897) was an American lawyer, judge and diplomat who served as U.S. Minister to the Netherlands. He was the son of William L. Dayton.

Biography William Lewis Dayton Jr. was born in Princeton, New Jersey on April 13, 1839. He graduated from Princeton University in 1858, studied law and became an attorney.Walter Romeyn Benjamin, The Collector: A Monthly Magazine for Autograph and Historical Collectors, Volume 12, Issue 4, (January, 1899), page 40

A Republican, from 1861 to 1865 he served as a Secretary at the U.S. Embassy in Paris when his father was U.S. Ambassador to France. From 1865 to 1868 he served as Secretary to Governor Marcus Lawrence Ward.T. F. Fitzgerald, Manual of the Legislature of New Jersey, 1897, page 294

The younger Dayton was elected to the Trenton City Council in 1876 and served as Council President from 1876 to 1877. From 1879 to 1881 he was Trenton's City Solicitor.John Howard Brown, Lamb's Biographical Dictionary of the United States, Volume 2, 1900, page 394

In 1882 Dayton was appointed Minister to the Netherlands, serving until 1885.Hartford Courant, , April 22, 1882 He served again as Trenton City Solicitor from 1889 to 1891. He was appointed a Judge of the New Jersey Court of Appeals in 1896 and served until his death.Rossiter Johnson, John Howard Brown, The Twentieth Century Biographical Dictionary of Notable Americans, 1904, page 1898

Dayton was a founder of Mercer Hospital, Counsel and a board of directors member for the Trenton Banking Company, a member of the Trenton Battle Monument Association, manager of the Trenton Saving Fund Society, and President of the Board of Trustees of Trenton's First Presbyterian Church.Trenton Banking Company, The Trenton Banking Company: A History of the First Century of its Existence, 1907, page 107New York Times, Trenton's Battle Monument, October 20, 1893

Dayton died in Trenton on July 28, 1897.New York Times, Death List of a Day, July 29, 1897

William L. Dayton Jr. was married to Harriet Maria Stockton, the daughter of Robert F. Stockton and niece of John P. Stockton.Daughters of the American Revolution, Lineage Book, Volume 10, 1899, page 77Hamilton Schuyler, A History of St. Michael's Church, Trenton, 1926, page 290New York Times, Death Notice, Mrs. William L. Dayton, November 30, 1937New York Times, Death List of a Day, May 6, 1898

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