Karen Hargrave (plaintiff) and Paul Duval lived together for approximately 14 years before Duval’s death. Hargrave and Duval lived at various times in South Dakota and Oklahoma, among other states. Although Hargrave and Duval held themselves out as husband and wife, they were never formally married. Duval did appoint Hargrave as his health-plan beneficiary and granted Hargrave his power of attorney. When Duval died, Hargrave filed a petition in circuit court to be declared Duval’s surviving spouse under the common law for purposes of inheriting from Duval’s estate. The petition was opposed by Duval’s daughters (defendants). South Dakota did not recognize common-law marriage, but Oklahoma did recognize such marriages. At trial, Hargrave testified that she and Duval had an implicit agreement to be married. Hargrave explained that she and Duval never made a formal agreement to be married but at some point merely decided they were married. The circuit court found that a valid common-law marriage between Hargrave and Duval existed in Oklahoma. Accordingly, the circuit court recognized the marriage in South Dakota and granted Hargrave’s petition. Duval’s daughters appealed.