Sooners is the name given to settlers who entered the Unassigned Lands in what is now the state of Oklahoma before the official start of the Land Rush of 1889. President Benjamin Harrison officially proclaimed the Unassigned Lands open to settlement on April 22, 1889. As people lined up around the borders of the Oklahoma District, they waited for the official opening. It wasn't until noon that it officially was opened to settlement. The name derived from the "sooner clause" of the act, which stated that anyone who entered and occupied the land prior to the opening time would be denied the right to claim land.
According to the Encyclopedia of Oklahoma History and Culture, the designation Sooner initially had a very negative connotation. However, the negative connotation began to change by the time of statehood, and is no longer considered negative by most residents. In 1908, University of Oklahoma football team adopted the nickname "Sooners." The U.S. state of Oklahoma has been popularly nicknamed the "Sooner State" since the 1920s.
Sooners were often deputy marshals, land surveyors, railroad employees, and others who were able to legally enter the territory early. Sooners who crossed into the territory illegally at night were originally called "moonshiners" because they had entered "by the light of the moon." These Sooners would hide in ditches at night and suddenly appear to stake their claim after the land run started, hours ahead of legal settlers.
The term Boomer relating to Oklahoma refers to participants in the "Boomer Movement," white settlers who believed the Unassigned Lands were public property and open to anyone for settlement, not just Native American tribes. Their reasoning came from a clause in the Homestead Act of 1862, which said that any settler could claim 160 acres (0.65 km2) of public land. Some Boomers entered and were removed more than once by the United States Army.