April 22, 1889
The land run of 1889 began the legal opening of federally held land to white settlement. President Benjamin Harrison authorized the settlement of the Unassigned Lands of Indian Territory to whites, setting the stage for similar openings of land that had been granted to tribes. This land run set the stage for the creation of the Oklahoma Territory in the Organic Act of 1890.
Read more about the 1889 Land Run at the Encyclopedia of Oklahoma History and Culture.