Zebra Swallowtail

I saw this butterfly fluttering around my gazebo a few days ago and decided to take some pictures of it.  I only had my cellphone to take the pics with, and it is a very old Nokia (dumb) phone.  So I apologize for the poor quality of the pictures.

I don't remember ever seeing a butterfly like this one before.  From what I can gather looking online, it is a zebra swallowtail.  The swallowtail shape is new to me.  It just seemed so odd that it's wing are so wide at the top and so narrow at the bottom.  Just not what I think of when I think butterfly.