Sector 28
Sector 28 is one of the sectors of the United Sectors of North America. Belgian Vicky has a shirt that says "Don't hate on Sector 28," with the shape of the sector surrounding the numerals "28."
The shape of Sector 28 is identical to that of Texas from the 20th and early 21st century. Texas was the 28th state admitted to the union. As of Chapter 9 it is not yet confirmed whether the sector number is a coincidence.