The oozing, peat-covered area of the spring quivered when walked upon, and cattle sometimes became mired in it. Out of curiosity, Coplen probed the bog with a long pole and struck something hard. With the help of his brothers, he attached a hook to the pole and began hauling up bones, first an enormous vertebra, next a shoulder blade. Realizing they had uncovered something major, the Coplens soon drained the bog, bringing to the surface an amazing haul of huge and puzzling bones.
The five Coplen brothers, familiar with farm livestock, at least could match most of the bones with those of known animals, but could not identify the much larger creatures from which they must have come. Of all the bones uncovered, the most puzzling were the long, curved objects that the Coplens assumed to be huge horns. One weighed 145 pounds and was 10 feet long. Soon the brothers went on the road to exhibit some of their finds in such towns as Colfax, Walla Walla, and Dayton, where they attracted crowds and much newspaper coverage. A Colfax schoolteacher, James Edmiston, first posited the elephant connection and asserted that the long "horns" were actually tusks. In Dayton, an amateur photographer sent pictures of the bones to Yale University geologist James Dwight Dana, who authenticated them as belonging to "the extinct American elephant or mammoth" (Visible Bones, 80).
After their initial tour, the Coplens returned home to do more excavations and unearthed additional bones, bringing the tusk total to nine, ranging from three to 12 feet in length. In August, they launched a second, more ambitious tour, transporting the bones by steamship to The Dalles and Portland, where again they attracted crowds and newspaper comment. In Salem, Oregon, Thomas Condon, geology professor at the new university in Eugene, declared the fossils to be "unquestionably the finest elephant remains ever unearthed on this Coast" (Visible Bones, 82).
Meanwhile, Ben Coplen's neighbors, William and Thomas Donahoe, drained a spring on their own property and brought up, among other bones, a huge skull. They exhibited their finds at the Walla Walla County Fair. Finding the profits disappointing, they sold their bones to Nathaniel Thwing and his partners, who competed with the Coplens in exhibiting rival sets of fossils, showing them as far away as San Francisco.
In 1878, paleontologist Edward Cope of Philadelphia purchased the bones taken to San Francisco, including the gigantic skull. He later sold them to the American Museum of Natural History in New York, where they have helped researchers determine the different species of mammoths that once roamed North America.
In October 1876, the Coplens leased their traveling exhibit to Pacific University in Forest Grove, Oregon, in exchange for tuition for young George Coplen at Tualatin Academy. Tualatin was the preparatory school attached to the university.
In 1886, the Chicago Academy of Sciences purchased many of the remaining Coplen bones and assembled a skeleton comprised of the actual mammoth bones plus missing pieces made of plaster. The full mount was 13 feet high. In 1893 it was the central attraction at the Washington Pavilion at the World's Columbian Exposition in Chicago. In 1914 the Field Museum of Natural History in Chicago purchased the skeleton. There, paleontologists have studied it over the years and remounted it, most recently in 1993 for exhibition in its central hall. Later excavations of the Coplen and Donahoe sites produced some fossils of various animals, but nothing to compete with the mammoth discoveries of 1876.