The blue area is New York State; the red area is area code 585.
Area code 585 is the area code for Rochester and eight surrounding counties in western New York. It was created on November 15, 2001 in a split from area code 716. Previously, Rochester had shared 716 with Buffalo. Aside from new area codes created in the New York City metropolitan area and Long Island, 585 was the second new area code in New York since 1954, having been preceded by 845.
The border between 716 and 585 roughly matches county lines (without regard to mailing address) which causes confusion where a ZIP code overlaps a municipal boundary. Therefore, some ZIP codes have phone numbers in two area codes. Among these places: Akron, Alden, Arcade and Cuba. A significant part of Ontario County uses 315/680. Part of the town of Farmington is north of the NY Thruway (Interstate 90), and is "joined" with Wayne County in the 315/680 area code.