The panhandle didn't become part of Oklahoma until 1890. Prior to that, it was part of the Texas territory until Texas became a state, then public land/No man's land (settlers/military headed west crossed it, but no one settled it) until sometime in the 1860s when herders, hunters, and ranchers used the land until the 1880s when the first (white) settler arrived. In 1885, it was declared that no man's land was not Indian territory and a few settlements popped up, but no state claimed it. It was even divided into counties, and since no state claimed it, the folks there named it Cimmaron Territory. In 1889, most of the folks left to participate in the territory run in Oklahoma, and the panhandle later became part of the Oklahoma Territory in 1890. So yes, after the government said that no man's land wasn't Indian territory, whites settled there before the land rush. But it wasn't actually part of Oklahoma until after 1889.