Neb. Rev. Stat. § 22-208

Whenever any county seat shall be located upon any public lands of the United States, it shall be the duty of the county board to enter or purchase a quarter section of land at the place so designated, at the expense of and for the use of the county, within three months thereafter, if the land be subject to private entry; if not, the board shall claim the same as a preemption under the laws of the United States, for the use of the county.