Rev. Pierre DeSmet (1801-1873) was born in Belgium but came to America in 1821, joined by the Jesuit Society and began his work with the Indians. In his work, he established 16 treaties, crossed the ocean 19 times and traveled 180,000 miles on his errands of charity for the Indians who knew him as "The Sincerest Friend". On July 5, 1840, in the presence of 2,000 Indians, trappers and traders he offered the first Holy Mass in what is now Wyoming on an alter of native stone decorated with wild flowers. In Father DeSmet's own words: "It was a spectacle truly moving to the heart of a missionary that his immense family, composed of so many different tribes should prostrate themselves in equal humility before the "Divine Host." The monument of this site was erected in 1925 and a commemorative Mass is offered in July. On July 4, 1940, the 100th anniversary of the first Mass, a Pontifical high mass was offered by the Most Rev. Bishop McGovern assisted by more than 30 priests and attended by about 2000 people.