ZIP Code 03857

03857 is one of New Hampshire's ZIP codes, delivering to addresses in Newmarket, Rockingham County.

City: Newmarket
County: Rockingham County
State: New Hampshire
Prefix: 038xx

Where this code sits

03857 is part of the 038xx range, the group of codes handled by one mail processing centre. It is the only ZIP code delivering to Newmarket.

Newmarket New Hampshire ZIP codes →

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 03857 delivers to without sharing its boundary.

603 Area code 603

ZIP codes nearest 03857

The ZIP codes whose reference points sit closest to 03857.
ZIP code	Distance	Delivers to
ZIP code 03856	2.7 mi	Newfields, NH
ZIP code 03824	3.6 mi	Durham, NH
ZIP code 03861	3.8 mi	Lee, NH
ZIP code 03885	4.6 mi	Stratham, NH
ZIP code 03843	5.5 mi	Hampton, NH
ZIP code 03840	6.0 mi	Greenland, NH
ZIP code 03833	6.3 mi	Exeter, NH
ZIP code 03042	6.5 mi	Epping, NH

Straight-line distance between place reference points, not driving distance. Where a place has no Census Gazetteer point, its postal centroid is used instead.

Each point is the reference point for 03857, plotted from its record coordinates.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Scope ZIP code 03857. Source GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated 15 July 2026. A ZIP code is a set of delivery routes, not an area; the point shown is a record coordinate, not a centre.