County profile · official public datasets

San Miguel County, CO

59 public highway bridges tracked in the FHWA National Bridge Inventory: 54.2% rated Good, 42.4% Fair, 3.4% Poor.

59
Public bridges: 54.2%
Good condition: 3.4%
Poor condition

The verdict

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

San Miguel County pairs a better-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 41%
lowest Poor share in state: 3.4%
Poor-condition share: 59
public highway bridges: 1987
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.

San Miguel County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, San Miguel County ranks #26 of 64 Colorado counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 3.4%). San Miguel County, Colorado contains 59 public highway bridges. Roughly 54.2% are rated “Good,” 42.4% “Fair,” and 3.4% “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

Public highway bridges in San Miguel County

Good condition

54.2%

32 of 59 rated 7-9

Fair condition

42.4%

25 of 59 rated 5-6

Poor condition

3.4%

2 of 59 rated 4 or below

In-state Poor-share rank

#26 of 64

Among Colorado counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 59 NBI-tracked bridges by lowest applicable component rating.

Good

54.2% (32)

Fair

42.4% (25)

Poor

3.4% (2)

San Miguel County's Poor-condition bridges carry 999 vehicle crossings a day

That is 2.7% of the county's reported daily bridge traffic on 3.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 500 crossings a day against 376 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 58 of 59 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

20.3% of San Miguel County's bridges have passed the 50-year mark

12 of the 59 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 54.2% 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 83.4% of the county's Poor-condition bridge traffic

CITY ST - MAHONEY over SAN MIGUEL RIVER, built 1995, carries 833 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 2-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 999 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1930s

2
1940s

1
1950s

4
1960s

5
1970s

3
1980s

11
1990s

21
2000s

6
2010s

6

What this shows Construction peaked in the 1990s, when 21 of the county's bridges still in the inventory were built, which is 35.6% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year is 1987, 5 years newer than the Colorado average of 1982.

How San Miguel County compares with Colorado's closest counties by inventory size

The 5 Colorado counties nearest San Miguel County in number of bridges, with their condition splits. Its 3.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1987 against a peer-group mean of 1979 is 8 years newer.

Showing the 5 closest of 63 Colorado counties eligible for comparison.

Bridge inventory size and condition shares for San Miguel County and the 5 Colorado counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Conejos County	62	38.7%	46.8%	14.5%	1976
Pitkin County	62	38.7%	58.1%	3.2%	1985
Cheyenne County	61	57.4%	42.6%	0%	1978
Montezuma County	61	27.9%	63.9%	8.2%	1978
San Miguel County (this page)	59	54.2%	42.4%	3.4%	1987
Summit County	57	22.8%	71.9%	5.3%	1980

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 San Miguel 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 San Miguel County, both outside Colorado so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside CO (59 bridges here).

Glades County, FL · 59 bridges
Red Lake County, MN · 59 bridges
Washington County, NC · 59 bridges
Marion County, TX · 59 bridges

Similar average build year

Nearest mean year-built outside CO (1987 here).

St. Louis County, MO · avg 1987 · 912 bridges
Ellis County, TX · avg 1987 · 691 bridges
St. Louis County, MN · avg 1987 · 663 bridges
Palm Beach County, FL · avg 1987 · 610 bridges

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

All 59 Good 32 Fair 25 Poor 2

Good-condition bridges (32)

Sort:

San Miguel County Bridge Snapshot

Condition distribution

San Miguel County's Poor-condition bridges carry 999 vehicle crossings a day

20.3% of San Miguel County's bridges have passed the 50-year mark

One structure carries 83.4% of the county's Poor-condition bridge traffic

How San Miguel County compares with Colorado's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (32)

WINDING FOREST RD.

ARIZONA DRIVE

COUNTY ROAD G49

COUNTY ROAD M44

BENCHMARK DRIVE

SH 145 ML

COUNTY ROAD L63

COUNTY ROAD 19Q

COUNTY ROAD 63J

CARHENGE

TOWNSEND STREET

POLECAT LANE

COUNTY ROAD 57P

COUNTY ROAD 19Q

CITY ST.-COLUMBIA

BENCHMARK DRIVE

COUNTY ROAD 31U

COUNTY ROAD L63

COUNTY ROAD 13R

COUNTY ROAD 16R

COUNTY ROAD 19Q

COUNTY ROAD 63L

COUNTY ROAD 60M

COUNTY ROAD M44

MTN VILLAGE BLV

COUNTY ROAD 56V

CITY ST - MAPLE

ADAMS RANCH RD

COUNTY ROAD U29

SNOWDRIFT LANE

HOOD PARK ROAD

MTN VILLAGE BLV

Related