The first 100 was shot at the 1910 GAH in Chicago by Riley Thompson, at 19yds. using a Parker
http://www.la84foundation.org/Sports.../SL5517024.pdf
"Riley Thompson is from Cainesville, Missouri, and the fact that Harvey McMurchey had finished his 100 with only one down did not bother the "Show Me" at all. He took his place for the last round, and paying no attention to the large crowd which still remained for the finish, proceeded to smash target after target, until the referee called "dead” for the twentieth, when the shooters rushed, lifted him on their shoulders and carried him to the club house, where he was surrounded by those anxious to shake his hand. Among the first to tender congratulations was Harvey McMurchey, who was runner-up with 99. J. Graham, Long Lake, Ill., (who won the Gold at the 1912 Olympics using a Remington pump) and Geo. Volk, Toledo, O., were in third place with 98 each."