Area code 721
Sint Maarten became a NANP territory on September 30, 2011, after having been approved for membership in 2009. Previously, Sint Maarten used the country code +599, originally assigned to the now-dissolved Netherlands Antilles and still in use by Curaçao and the Caribbean Netherlands (Bonaire, Sint Eustatius, and Saba). The northern French side of the island, known as Saint-Martin, is not within the North American Numbering Plan, and has the country code +590, shared with Guadeloupe and Saint Barthélemy. Calls between the two parts of the island are international calls.
A one-year permissive dialing period was granted when either the old country code or the new area code could be used for dialing calls to Sint Maarten, after which use of +1 721 became mandatory.
On July 27, 2011, a new Planning Letter, #423, was issued by NeuStar NANPA, which indicates that the implementation of +1 721 for Sint Maarten had been granted, with implementation dates set for September 30, 2011 for permissive dialing and September 30, 2012 for mandatory dialing. Previous planning letters indicated other implementation dates, but those were superseded by the July 2011 planning letter.
Calling procedure 
Callers from outside of the NANP (country code +1), including callers from the French side of the island, must dial their international access code (often 00) followed by 1 721. Callers within the NANP dial 1 721 and the seven-digit telephone number.
Previous code 
The remaining portions of the former Netherlands Antilles (Curaçao and the Caribbean Netherlands) are retaining country code +599 for the present time. At this time, no known plans exist for these other islands to either join the NANP or adopt their own separate country codes.
See also 
- List of NANP area codes
- Area codes in the Caribbean
- Telephone numbers in Aruba
- Telephone numbers in Curaçao and the Caribbean Netherlands
- Telephone numbers in the Netherlands