When General Robert E. Lee's invading army overran the Union garrison at Winchester, Virginia, on June 15, 1863, elements of the 1st New York "Lincoln" Cavalry covered the retreat. Company C, under Captain William Boyd, continued to harass the Confederates as they crossed into Pennsylvania. On June 22, Boyd's 35 men narrowly avoided an ambush at the William Fleming farmhouse. When Corporal William Rihl, a 21-year-old Philadelphia native, and Sergeant Milton Cafferty rode out in front of the house to reconnoiter, the Confederates fired a volley at point-blank range. Cafferty suffered a serious leg wound; Rihl was struck in the head and died instantly, the first Union soldier killed on Pennsylvania soil.
The events at Gettysburg soon overshadowed the skirmish at Fleming farm, but the people of Greencastle remembered, as did the veterans of the 1st New York Cavalry. On June 22, 1886, Greencastle's G.A.R. Post 438 reburied Rihl with full military honors at the spot where he fell. Exactly one year later, Pennsylvania's state legislator erected a monument over Rihl's new grave, honoring him as "a humble but brave defender of the Union."