Why are the people of Oklahoma called “Sooners”?

In the 1800s, when the American West was first opened, the early pio-
neers were offered free land east of the Rockies, but to ensure fairness,
they could only stake out forty acres after a race to the region on a spe-
cific date and time. Those heading for Oklahoma who jumped the gun
and settled on the best land before the official start of the race were
cheating and were called “Sooners” because they arrived “sooner” than
those who obeyed the law.