631 Area Code: Brentwood, New York

Suffolk County on eastern Long Island is served by the 631 area code, with Brentwood as the primary city in the directory's records. Brentwood sits in central Suffolk County, on a stretch of inner Long Island that has filled in heavily through the postwar decades. The 631 footprint covers Suffolk County in its entirety, taking in Smithtown, Babylon, Huntington, Riverhead, the Hamptons on the East End, and the cluster of incorporated villages and unincorporated communities that fill out the eastern half of Long Island. The 631 designation has carried Suffolk County's numbers since it was carved out of the older Long Island numbering in the late 1990s.

Records linked to 631 numbers in the directory often include Albany, Binghamton, Buffalo, and Hempstead — New York cities outside the 631 footprint. The pattern reflects standard public-record dynamics, with phone numbers porting across New York and addresses linked across multiple cities. The directory currently documents 591 distinct prefixes within 631 in detail, a working subset of the prefix population the code carries.

Brentwood's median household income runs well above the US figure, in line with the broader Long Island corridor's higher-income profile. Home values come in well above the national median, the city's median age sits close to the US reading, and population places Brentwood among the larger census-designated places in New York. The 631 footprint as a whole reflects an unusually high overall demographic profile relative to most of the country, with sharp variation between the inner-Suffolk communities, the Hamptons-area resort towns, and the working farms and fishing communities at the East End.