Cherokee allotment records are digitized on Ancestry. Once you know the location of an allotment you need to determine what Oklahoma county it was located in. Then the Registry of Deeds for that county would have the records to show when the land was sold and to whom. Cherokee who were more than half-blood had restrictions on their land and any sales or transfers before 1928 should be noted in the allotment record. After 1928 the restrictions were lifted and transfers were like any other property transaction.