MONROE- It's but one small sign that the area's growing. Starting on Dec. 1, more than 1,700 people and businesses renting Post Office boxes at the Monroe Post Office got a new ZIP Code. No longer should their mail read: Monroe, N.Y. 10950. It's now Monroe, N.Y. 10949. The box numbers did not change and the Postal Service assures that there won't be an interruption in service. Just the ZIP Code: 10949. The Postal Service's Westchester district found it necessary to make the change due to residential and business growth as well as the creation of new addresses. And, notes Monroe Postmaster Joe Curto, he and his people are ready for more because the Monroe Post Office has additional boxes available for rent. Postal Service officials will continue to deliver to the box holders under the old ZIP Code for a year. Residents and businesses of Monroe with door or curbside delivery service will keep their current ZIP Code 10950. The change does not affect them. There are now 62 ZIP codes in Orange County, says Postal Service spokeswoman Patricia McGovern. The last time there was an addition was several years ago when the greater Middletown area expanded from simply 10940 to 10941.