What administrative division is RDU airport actually located in?

Raleigh-Durham International Airport claims to have a physical address in Morrisville NC 27560, but a mailing address in "RDU Airport, NC 27623", and yet Wikipedia says that it is in Cedar Fork Township, Wake County and is 9 miles northeast of Morrisville (rather than saying it's "in" Morrisville). Other sites on the Web say that RDU Airport is in Morrisville. I don't get it. Is RDU Airport actually located within the borders of a town or city, or not? What kind of political "division" does RDU Airport really technically fall in, and why is there so much ambiguity over whether it is actually in or outside of Morrisville?