A number of different websites list all of the area codes in the United States, including AreaCode.org and AllAreaCodes.org. Both websites list the area codes sequentially starting with the lowest numbered area code to the highest.
Both AreaCode.org and AllAreaCodes.org also feature a list of area codes by location, an area code search feature, as well as an area code list in printable format. Other websites such GreatData.com include time zone information when listing area codes. The Wikipedia article on area codes includes numbers reserved for special use. For instance, the Wikipedia article contains information on area codes 800, 888, 877 and 866; these are area codes that have been designated as toll free exchanges as of 2015, meaning that the party receiving the call is charged.
Area codes are assigned according to the North American Numbering Plan, which assigns area codes not only for the United States but for 20 other countries, primarily in North America. Area codes have seen rapid expansion since 1996 to meet increasing demand due to new telephone services such as fax, modem and mobile lines. The demand is so high that a proposed plan seeks to increase the area code designation from 3 digits to 5 digits.