Sooners were settlers who illegally entered the Unassigned Lands of Indian Territory, now Oklahoma, before the official start of the Land Rush of 1889 on April 22. President Benjamin Harrison proclaimed the land open, but a "sooner clause" explicitly denied claims to those who entered early, giving the term a negative connotation for cheating other land-seekers. Unlike "Boomers" who legally lobbied for the land's opening, Sooners, sometimes called "moonshiners" for entering at night, would hide and stake prime claims hours ahead of legitimate participants. These actions led to widespread disputes and litigation well into the 20th century, eventually settled by the U.S. Department of the Interior. Despite their controversial origins, the term's negative perception cooled over time, leading the University of Oklahoma to adopt "Sooners" as its athletic nickname in 1908, and the state itself is now colloquially known as "The Sooner State."