When was Merrimack County founded?

Merrimack County was founded in 1823, formed from Hillsborough County and Rockingham County, and named after Merrimack River, New Hampshire and Massachusetts.

What is the county seat of Merrimack County?

The county seat of Merrimack County is Concord.

Is there an online parcel map for Merrimack County?

Yes. New Hampshire Geographic Information System Clearinghouse (GRANIT) publishes a parcel map of 65,588 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Merrimack County's boundary or name changed?

Merrimack County was created in 1823 from Hillsborough County and Rockingham County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Grafton County and Strafford County.

Is my lot in a flood zone?

We do not have flood maps for Merrimack County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

County · code 33013

Merrimack CountyNew Hampshire

Merrimack County is a county in New Hampshire, with its seat in Concord. It was founded in 1823 from Hillsborough and Rockingham counties and named after the Merrimack River.

Founded1823
County seatConcord
Named forMerrimack River, New Hampshire and Massachusetts
Land area933 sq mi + 22 sq mi water
Population153,808 2020 Census
Parcels mapped65,588 checked 14 October 2026

Open the free map Click any parcel in Merrimack County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 19 October 2026

Census outline · seat marked

Where it is

Merrimack on the map of New Hampshire

New Hampshire has 10 counties and county equivalents, each with its own records office. Shapes with a page are links.

Counties of New Hampshire · Merrimack highlighted

History

Formed in 1823 from Hillsborough County and Rockingham County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Merrimack County was created from Hillsborough and Rockingham in 1823. It gained territory from neighboring counties over several decades: from Strafford in 1828 when Franklin was created, from Grafton in 1832 when Wilmot gained from New Chester, and additional towns from Grafton in 1868 and 1874.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries.

1823
Merrimack County created Merrimack created from Hillsborough and Rockingham.
from Hillsborough from Rockingham
1 August 1823 · N.H. Early Laws, vol. 9, ch. 38 [1823], secs. 2, 12/pp. 221, 224
1828
Gained territory Merrimack gained from Strafford when town of Franklin was created from towns of Andover, Northfield, Salisbury, and Sandbornton.
from Strafford
24 December 1828 · N.H. Early Laws, vol. 9, ch. 62 [1828], sec. 1/pp. 784-786
1829
Boundary clarified Merrimack boundaries were redefined (no change).
no change
2 January 1829 · N.H. Early Laws, vol. 9, ch. 100 [1829], sec. 1/pp. 879-882
1832
Gained territory Merrimack gained from Grafton when town of Wilmot gained from town of New Chester (now Hill).
from Grafton
21 December 1832 · N.H. Early Laws, vol. 10, ch. 19 [1832], secs. 1-2/pp. 365-366
1868
Gained territory Merrimack gained town of Hill from Grafton.
from Grafton
1 July 1868 · N.H. Laws 1868, ch. 14, sec. 1/p. 148
1874
Gained territory Merrimack gained town of Danbury from Grafton.
from Grafton
10 July 1874 · N.H. Laws 1874, ch. 96, sec. 1/p. 338

Land and parcels

What the maps cover in Merrimack

Who publishes each layer, how good it is, and when we last checked.

Parcels Good enough

Lot lines and tax-map numbers for 65,588 parcels from New Hampshire Geographic Information System Clearinghouse (GRANIT). Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 14 October 2026
Address points Missing

No public address points layer found for Merrimack County yet.
Buildings Reference

Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026

Official: from the office that keeps the record
Good enough: a reliable statewide or national copy
Fallback: a guide only; check the official record
Missing: nothing public found yet

People and land

Merrimack by the Census

Population

153,808 2020 Census count

Housing units

65,565 2020 Census count

Land area

933 square miles

Water area

22 square miles

People per sq mi

165 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

In New Hampshire, permits, zoning and assessing are handled by each city or town, not the county, and deeds are recorded at the county's registry of deeds.

Records

Clerk of court: deeds and plats
Staff Directory
from merrimackcounty.net · checked 13 October 2026

County government

County government
The official website of Merrimack County.
merrimackcounty.net

See your own lot on these maps

Open Merrimack County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

Open the free map no sign-in Pro early access

Questions

Common questions about Merrimack County

When was Merrimack County founded?: Merrimack County was founded in 1823, formed from Hillsborough County and Rockingham County, and named after Merrimack River, New Hampshire and Massachusetts.
What is the county seat of Merrimack County?: The county seat of Merrimack County is Concord.
Is there an online parcel map for Merrimack County?: Yes. New Hampshire Geographic Information System Clearinghouse (GRANIT) publishes a parcel map of 65,588 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Merrimack County's boundary or name changed?: Merrimack County was created in 1823 from Hillsborough County and Rockingham County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Grafton County and Strafford County.
Is my lot in a flood zone?: We do not have flood maps for Merrimack County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby