The Great Oklahoma Land Run

The Oklahoma Land Run of April 22, 1889 was one of the most chaotic and extraordinary events in American history. At precisely noon, a pistol shot signaled the opening of two million acres of unassigned land in Indian Territory to settlement, and an estimated 50,000 people who had been waiting at the border simultaneously charged in on horseback, in wagons, and on foot to stake their claims. By nightfall, the city of Guthrie had a population of over 10,000 people. Settlers who had sneaked in before the official start and were hiding were called Sooners, which became the state's nickname.

Source: Wikipedia