Area code 866 is toll-free numbers, just like area codes 800, 888, 877, and 855, and future area codes 844, 833, and 822.
Toll-free codes are not associated with any particular city, state, or country. The person on the other end of the line could be anywhere in the world. 866 numbers are toll-free from landlines, but airtime charges will usually still apply for calls from a cellphone.
In North America (USA, Canada, etc.), area code 866 is used for toll-free numbers. The person on the other end of the phone could be anywhere in the world.
As of 2013, North American toll-free codes are 800, 888, 877, 866, and 855, with 844, 833, and 822 in reserve for future use.
Redwood City is in area code 650.
Missouri City is in area code 281, with overlay code 832. There may also be some Missouri City numbers in area code 713.
Traverse City, Michigan, is in area code 231.
Rockwell City, Iowa, is in area code 712.
The area code for the whole Davao City is 082.
Johnson City, NY, is in area code 607.
The area code 479 is for the state of Arkansas. A zip code is for a city or part of a city. By area code alone you cannot determine a zip code.
Gotham City is a fictional place, and thus has no actual area code.
It has the area code 082.
Area code 609 is in New Jersey, including Atlantic City, Trenton, and Princeton.
The 916 area code is assigned to the city of Sacramento which resides in California, U.S.A. An interesting fact about this area code is that it was one of the original area codes developed in 1947.
Area code 773 is an area code for Chicago, Illinois. The city was given this area code on October 12'th, 1996. Before this code the area code was 312, for the whole city until 708 was created for the suburbs only.