The eastern half of the state was prepping for statehood on its own, as the State of Sequoyah. Had a draft constitution and everything. Ultimately, the plan fell through and both territories became a state, although much of Oklahoma's constitution came from the what had been drafted for Sequoyah.
https://sites.rootsweb.com/~oktttp/IT/sequoyah/index.html
"The convention drafted a constitution, drew up a plan of organization for the government, put together a map showing the counties to be established, and elected delegates to go to the United States Congress to petition for statehood. Two of the “hot” topics of discusion of the convention were Woman Suffrage and prohibition. The Cherokee delegation wished to allow women the right to vote, but the rest were against it. The convention's proposals were put to a referendum in the Indian Territory, where they were overwhelmingly endorsed.
The Sequoyah delegation received a cool reception in Washington. Eastern politicians, fearing the admission of two more Western states, with a relative increase in political power, put pressure on the U.S. President, Theodore Roosevelt. He ruled that the Indian and Oklahoma territories would be granted statehood only as a combined state."
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