Mo. Rev. Stat. § 54.100: To keep office at county seat — county commission to provide vault.

The county treasurer shall keep his office at the county seat of the county for which he was elected, and shall attend the same during the usual business hours. The county commission shall provide said county treasurer with suitable rooms, and a secure vault in the courthouse or other building occupied by other county officers, and the county treasurer shall keep his office and records in such rooms and vault provided by the county commission. He shall receive all moneys payable into the county treasury, and disburse the same on warrants drawn by order of the county commission.