County profile · official public datasets

Grafton County, NH

544 public highway bridges tracked in the FHWA National Bridge Inventory: 47.8% rated Good, 44.1% Fair, 8.1% Poor.

544
Public bridges: 47.8%
Good condition: 8.1%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Grafton County posts a higher-than-median Poor-condition share among rated counties in the state across large county bridge inventory.

7th
of 10 on Poor share: 8.1%
Poor-condition share: 544
public highway bridges: 1966
avg year built

Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.

Grafton County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Grafton County ranks #7 of 10 New Hampshire counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 8.1%). Grafton County, New Hampshire contains 544 public highway bridges. Roughly 47.8% are rated “Good,” 44.1% “Fair,” and 8.1% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.

Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.

Source: FHWA National Bridge Inventory. See methodology for full definitions.

Total bridges

544

Public highway bridges in Grafton County

Good condition

47.8%

260 of 544 rated 7-9

Fair condition

44.1%

240 of 544 rated 5-6

Poor condition

8.1%

44 of 544 rated 4 or below

In-state Poor-share rank

#7 of 10

Among New Hampshire counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 544 NBI-tracked bridges by lowest applicable component rating.

Good

47.8% (260)

Fair

44.1% (240)

Poor

8.1% (44)

Grafton County's Poor-condition bridges carry 137,215 vehicle crossings a day

That is 7.5% of the county's reported daily bridge traffic on 8.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 3,119 crossings a day against 3,685 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.

Computed over the 543 of 544 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

63.2% of Grafton County's bridges have passed the 50-year mark

344 of the 544 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 47.8% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.

Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.

One structure carries 16.2% of the county's Poor-condition bridge traffic

I-89 NB over US 4 NH 10, built 1966, carries 22,282 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 44-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 137,215 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

6
1900s

7
1910s

2
1920s

36
1930s

63
1940s

39
1950s

48
1960s

92
1970s

80
1980s

61
1990s

29
2000s

40
2010s

36
2020s

5

What this shows Construction peaked in the 1960s, when 92 of the county's bridges still in the inventory were built, which is 16.9% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1966) matches the New Hampshire average (1968).

How Grafton County compares with New Hampshire's closest counties by inventory size

The 5 New Hampshire counties nearest Grafton County in number of bridges, with their condition splits. Its 8.1% Poor share is the 4th-lowest of these 6. Its average build year of 1966 against a peer-group mean of 1968 is in line with the group.

Showing the 5 closest of 9 New Hampshire counties eligible for comparison.

Bridge inventory size and condition shares for Grafton County and the 5 New Hampshire counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Grafton County (this page)	544	47.8%	44.1%	8.1%	1966
Hillsborough County	385	51.4%	39.7%	8.8%	1972
Merrimack County	326	45.1%	46.9%	8%	1966
Rockingham County	308	66.6%	26.9%	6.5%	1977
Carroll County	193	54.9%	40.9%	4.1%	1966
Cheshire County	192	41.7%	46.9%	11.5%	1960

Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Grafton County's. Source: FHWA National Bridge Inventory, 2024 release.

Nationwide counties with similar inventory size or average build year

Two NBI-derived peer sets for Grafton County, both outside New Hampshire so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside NH (544 bridges here).

Polk County, IA · 545 bridges
Yavapai County, AZ · 543 bridges
East Baton Rouge County, LA · 548 bridges
Adams County, CO · 535 bridges

Similar average build year

Nearest mean year-built outside NH (1966 here).

Butler County, KS · avg 1966 · 591 bridges
Queens County, NY · avg 1966 · 514 bridges
Lehigh County, PA · avg 1966 · 381 bridges
Osage County, OK · avg 1966 · 366 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 544 Good 260 Fair 240 Poor 44

All bridges (544)

Sort:

Grafton County Bridge Snapshot

Condition distribution

Grafton County's Poor-condition bridges carry 137,215 vehicle crossings a day

63.2% of Grafton County's bridges have passed the 50-year mark

One structure carries 16.2% of the county's Poor-condition bridge traffic

How Grafton County compares with New Hampshire's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (544)

RIVER ROAD

BLAIR ROAD

BUMPS INTERVALE

PORTER ROAD

HAMMOND HILL ROAD

WEST BATH ROAD

RIVERSIDE DRIVE

RIVER STREET

FLUME BUS ROUTE

WINTER STREET

MILLBROOK ROAD

NO DATA ENTERED

NORTH GROTON ROAD

STINSON LAKE ROAD

DANIELS ROAD

NO DATA ENTERED

RUDDSBORO ROAD

US302 NH 10

CHASE ROAD

NH116

DOW AVENUE

RIDDLE HILL ROAD

SLAB CITY ROAD

WILD MEADOWS ROAD

NORTH SHORE ROAD

BISHOP ROAD

RIVER ROAD

BREEZY HILL ROAD

MARKET STREET

NH175

FDR 53

PEARL LAKE ROAD

NORTH DORCHESTER R

BRISTOL HILL ROAD

BREEZY POINT ROAD

ROADWAY

MCINDOES STREET

WEST BRANCH ROAD

NH112

ELLSWORTH HILL RD

NH175

DELAGE FARM ROAD

STINSON LAKE ROAD

FDR 22

FDR 92

FDR 203

US 4

NH118

NICHOLS HILL ROAD

DWYER ROAD

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