Area code 906 was formed in an area code split of numbering plan area (NPA) 616 on March 19, 1961. The split was implemented in a flash cut, with no permissive dialing period. 906 is among the least populous numbering plan areas in North America, serving only about 320,000 people. The latest NANP projections estimate the exhaustion of vacant central office codes for the 906 area code until the early 22nd century, meaning that the Upper Peninsula will not need another area code for several decades.[1] The area code has inspired an unofficial holiday in the Upper Peninsula on September 6 (906 correlating to the month/day date).[2]
Bois Blanc Township in the only municipality associated with the Upper Peninsula to not use area code 906. It is an island in Lake Huron whose only ferry service is with the closer Lower Peninsula, and therefore uses area code 231.
Most of the numbering plan area is in the Eastern Time Zone, except for the counties bordering Wisconsin, which are in the Central Time Zone.