Area codes 630 and 331, Telephone prefix in Illinois, United States.
Area codes 630 and 331 are telephone prefixes covering suburbs west of Chicago in Illinois. Both codes share the same geographic area and function as overlapping number ranges for calls in the region.
Code 630 emerged in 1996 from a split with the older area 708 to meet growing demand for phone numbers. Code 331 was introduced in 2007 and overlaid the existing territory so both prefixes now operate side by side.
These area codes connect diverse suburban communities within the Chicago metropolitan region, spanning residential neighborhoods and commercial districts.
Anyone calling a number within these prefixes must dial all ten digits, even for local calls. The overlap means new phone lines can receive either 630 or 331 depending on number availability.
The overlay system allows calls between all locations in this zone without extra charges, creating an unusually large area for local telephony. Some older phones without ten-digit dialing cannot reach these numbers directly anymore.
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