Iowa Code § 538.2
When a contract for labor, or for the payment or delivery of property other than money, does not fix a place of payment, the maker may tender the labor or property at the place where the payee resided at the time of making the contract, or at the residence of the payee at the time of performance of the contract, or where any assignee of the contract resides when it becomes due, but if the property in such case is too ponderous to be conveniently transported, or if the payee had no known place of residence within the state at the time of making the contract, or if the assignee of a written contract has no known place of residence within the state at the time of performance, the maker may tender the property at the place where the maker resided at the time of making the contract.
Iowa Code § 538.2