Wis. Stat. § 279.20: Investment authorization.

The bonds of the authority are securities in which all public officers and bodies of this state; all political subdivisions and their public officers; all banks, trust companies, savings banks and institutions, savings and loan associations, and investment companies; and all personal representatives, guardians, trustees, and other fiduciaries may legally invest any sinking funds, moneys, or other funds belonging to them or within their control.