Gray Territory (or Gray Zone) is a term for land and territory that fell under the control of the Chimera. All of Europe with the exception of Great Britain became gray by 1951. In August 1951, the New England states of the United States became the first American territory to fall under a Gray Zone in which propagandist organizations such as the Perception Protection and Guidance reassured the American public that the Gray Zones are still part of the United States if "all requirements have been met" by experts to assess the damage within a Gray Zone, this will be "upgraded" to "Inhabitable" status.
After SRPA's botched attempt to destroy the New York Tower, all forms of military presence disappeared and the Chimera proceeded to take over the U.S., turning the entire country into a Gray Zone as a result. However, by the end of Resistance 3, survivors are implied to be retaking territories.