Not an amaryllis! Looks like something from the Hymenocallis family.

Judging by the photos it is Ismene (Hymenocallis) Sulphur Queen. Compare my picture in the "Here in my garden blossomed..."

oleg8
I did see your post after I put mine up. I think you are correct. I live in sone 5, in Iowa. Should I treat it just like an amaryllis? Bring it in and let it go dormant for the winter or whenever it wants to get active?

* Should I treat it just like an amaryllis? *
No, not like hippeastrum or amaryllis. Ismene should be planted in spring after the frost in the garden. Digging is necessary to frost in the fall with the roots. Then dry and store in a cool (but not less than 10-15 C), dry place until the spring. Ismene have long period of dormancy. And before the April-May plants sprouts do not appear. This depends on the storage temperature. If warmer than the growth starts earlier.

Oleg gives excellent advice. If you want some more info on this interesting hybrid of H. narcissiflora (syn. Ismene narcissiflora), the Peruvian
Daffodil, and Hymenocallis amancaes, (syn. Ismene amancaes) go to the Pacific Bulb Society's website. Ismene 'Sulphur Queen'