S.D. Codified Laws § 55-1-20
Subdivisions 55-1-4(2) and 55-1-5(2) notwithstanding, a purpose trust may be performed pursuant to this section and §§ 55-1-21 to 55-1-22.6, inclusive, if the trust is for a lawful noncharitable purpose or purposes. Any property may form a part or all of the trust estate, including some, all, or an interest in some or all of the property that is the subject or purpose of a purpose trust. A governing instrument of such a trust shall be liberally construed in favor of its validity to presume against the merely precatory or honorary nature of the disposition and to carry out the trustor's intent. If necessary, extrinsic evidence is admissible to determine the trustor's intent. Neither the common law rule against perpetuities, nor any rule restricting the accumulation of income, nor any common law rule limiting the duration of noncharitable purpose trusts is in force in this state.
SDCL 55-1-20