My Plant is Flowering

I still don't know what this is, if an Iris or a lily or what.  All I know is that it takes years for it to bloom, and once it blooms, it does so once a year, one per plant.  I went about 20 years or so to the center of the island, to Orocovis, and we went up to the mountain, to a property that my father-in-law had.  His wife gave me a little plant.  I never knew what it would look like, but I'm glad i accepted it.

I don't know why the other plants are not flowering, though.  I think I'll transfer those to the front of the house, just to see what happens.