From 2404.org:
http://www.2404.org/news/1404/Age-of-Empires-III-v1.09-PatchEnsemble Studios has released a new patch for "Age of Empires III," bringing the real-time strategy game up to version 1.09.
"This patch adds several changes to increase the rate at which Home Cities advance in level, including new bonus experience awarded after each game you play."
The patch can be downloaded from the official site, us (local mirror), 3dgamers, FileFront, VGPro, or Worthplaying.