What Is This Plant?

I always like to let "weeds" grow in my yard long enough to identify them and decide if I really want them there or not. This year I have been caring for two that I can't identify. The first one grew about six feet tall. It has super tiny white flowers that look like they should open more, but haven't so I can't see how many petals they really have. The leaves a pretty long and stringy also. I pulled it up because its fragrance was wreaking havoc on my allergies.