Iowa Code § 589.28

All proceedings taken by the board of supervisors of any county pertaining to the sale of any property which was no longer needed for the purpose for which it was acquired or any other county purpose and sold pursuant to section 331.361, where the board failed to offer such property for sale at a public auction on or after June 30, 1974 and on or before July 1, 1975 are validated, legalized, and confirmed and shall constitute a valid, legal, and binding sale of such property sold on or after June 30, 1974 and on or before July 1, 1975 by the board of supervisors of any county.