Mo. Rev. Stat. § 12.040

Exclusive jurisdiction in and over any land acquired as set out in section 12.030 or otherwise lawfully acquired and held for any of the purposes set out in section 12.030 by the United States, is ceded to the United States for all purposes, saving and reserving, however, to the state of Missouri the right of taxation to the same extent and in the same manner as if this cession had not been made; and further saving and reserving to the state of Missouri the right to serve thereon any civil or criminal process issued under the authority of the state, in any action on account of rights acquired, obligations incurred, or crimes committed in this state, outside the boundaries of the land but the jurisdiction ceded to the United States continues no longer than the United States owns the land and uses the same for the purposes set out in section 12.030.