European Americans first mapped the site in the 1840s. The archaeologists Ephraim George Squier and Edwin Hamilton Davis were the first excavators of the site and amassed a large collection of Mound artifacts that is now preserved at the British Museum. Much of it was destroyed during World War I when the United States Army constructed a military training base, Camp Sherman, on the site. After the war, they razed the camp. The Ohio Historical Society conducted an archaeological excavation of the site from 1920–1922, followed by reconstruction of the mounds. In 1923, the Department of Interior declared the Mound City Group a National Monument, to be administered by the Federal government.