Born 7 Aug 1890, graduated Harvard 1912, newspaper correspondent in Mexico, enlisted in the French Foreign Legion Jan 1915, killed in action near Navarin Farm, France. The Farnsworth Room in the Widener Memorial Library at Harvard was donated by Mr. and Mrs. William Farnsworth, in memory of their son.
From the Dedham Tales Press website:

Henry Farnsworth of Westfield St. was one of the first American casualties of World War I, having died in the Battle of Champagne in September, 1915 while fighting with the French Foreign Legion.
Farnsworth attended Groton and Harvard, graduating in 1912. He lived a life of adventure in the short time between his graduation in 1912 and his death on the French battlefield, reporting from the Balkan War in 1912 and traveling to Mexico when U.S. troops arrived there in 1914. His exploits in the Balkans were published as “The Log of a Would-be War Correspondent.”
Farnsworth was working in the Boston office of his father, a wool merchant when war broke out in Europe. His need for adventure compelled him to sail to France and enlist in the French Foreign Legion on New Year’s Day, 1915. Soon his unit was on the front lines and in the trenches. He wrote this passage to his mother on March 15: “I long to be with you all again, once the war ends. I think it will be this summer some time; then for the rest and peace of Dedham.”
Farnsworth’s last letter home was dated September 16. On September 28, he was killed while fighting in the trenches outside of Champagne. Many of his fellow Legionnaires spoke of Henry Farnsworth’s remarkable spirit and bravery. His letters were later published by his father and can be found on Googlebooks.

In 1920, an elaborate monument was dedicated to the memory of Farnsworth and 130 other foreign Legionnaires killed in the Battle of Champagne. The monument was paid for by the Farnsworth family. The monument is located near the French town of Souain-Perthes-lès-Hurlus.
Farnsworth was also good friend with Victor Chapman of the Lafayette Escadrille.