The city of New Phoenix was incorporated at some point between the 21st and 26th-centuries as a merge of the Arizonan cities Flagstaff and Phoenix. By 2542,[notes 1] the city was the fourth-most populated in North America (behind Chicago, Los Angeles and New York, respectively).
New Phoenix was fired upon by the Ur-Didact's ship Mantle's Approach. Although the Ur-Didact was stopped by John-117, the city’s entire population was composed, leaving only ash where its inhabitants last stood.
- In Issue 7 of Halo: Escalation, SPARTAN Thorne mentions that New Phoenix was formed as a merger of the 19th-century cities of Flagstaff and Phoenix. As of 2014, these cities are 144 miles (233 kilometers) distant, allowing New Phoenix's geographic size to be approximated.
- Despite the size of the city and the fact that it is the fourth-most populous city in the United Republic of North America, in Halo: Escalation it is mentioned that at the time of the New Phoenix Incident the city was home to a mere six million inhabitants. This is curious, seeing as the next most populous city is Chicago, with a population of 54 million.