Find any 840- phone number in California

The 840 area code is a part of the North American Numbering Plan. This system is used to assign telephone numbers throughout the US, Canada, and the Caribbean. 840 is a three-digit geographic area code that is used to designate a specific location within the United States. The 840 area code primarily covers portions of North Dakota, but also covers parts of Wyoming, Montana, Idaho, and South Dakota.

The North American Numbering Plan was first established in 1947 as a way to standardize telephone numbers throughout the US, Canada, and the Caribbean. This system is a useful way to identify a particular geographic area and simplify calls between different regions. Each area code is composed of a three-digit code, followed by a three-digit prefix and a four-digit line number. Together, this seven-digit combination is used to identify the number's calling area. In the 840 area code, the prefix is typically used to distinguish areas of the state, while the line number is specific to an individual phone number.