USCIS - Application to Register Permanent Residence or Adjust ...
Where you file your Form I-485 depends on what eligibility category you are part ... (e) (and K-2 dependents) whose Form I-485 is based on an approved Form ...
http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=3faf2c1a6855d010VgnVCM10000048f3d6a1RCRD&vgnextchannel=db029c7755cb9010VgnVCM10000045f3d6a1RCRD