I am guessing one of the species of either Nicotiana mutabilis (flowering Tobaco plant) or species of Mirabilis jalapa (Marvel of Peru, Four O'Clock Flower)
I'd say a phlox. See the unopened buds? They have spiral stripes? That is distinctly phlox-like. I am not familiar with the species Carolina Phlox (I live too far north) but Palustris might be right its being a Carolina. I have grown a Carolina phlox cultivar, 'Miss Linguard' & it had a lovely white flower. It was also not susceptible to mildew, a big plus. Perhaps that is true of the species Carolina too? Do you know @Palustris ?
Looks very much like the one I have which is just labelled P carolina, no cultivar name. Could be one called Kim, but that may be a bit more blue than this one.
