Iowa Code § 192.143: Imitation butter.

Imitation butter shall be sold only under the name of oleomargarine, and no person shall use in any way, in connection or association with the sale or exposure for sale or advertisement of any such product, the word “butter”, “creamery”, or “dairy”, or the name or representation of any breed of dairy cattle, or any combination of such word or words and representation, or any other words or symbols or combination thereof commonly used in the sale of butter.