Total bridges
124
Public highway bridges in St. Mary County
County profile · official public datasets
St. Mary County, LA
124 public highway bridges tracked in the FHWA National Bridge Inventory: 31.5% rated Good, 62.1% Fair, 6.5% Poor.
- 124
- Public bridges
- 31.5%
- Good condition
- 6.5%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
St. Mary County pairs a top-quartile lowest Poor-condition share among rated counties in the state with an older average build year than the state inventory.
- Top 19%
- lowest Poor share in state
- 6.5%
- Poor-condition share
- 124
- public highway bridges
- 1975
- 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.
St. Mary County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, St. Mary County ranks #12 of 64 Louisiana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.5%). St. Mary County, Louisiana contains 124 public highway bridges. Roughly 31.5% are rated “Good,” 62.1% “Fair,” and 6.5% “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.
Good condition
31.5%
39 of 124 rated 7-9
Fair condition
62.1%
77 of 124 rated 5-6
Poor condition
6.5%
8 of 124 rated 4 or below
In-state Poor-share rank
#12 of 64
Among Louisiana counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 124 NBI-tracked bridges by lowest applicable component rating.
Good 31.5% (39)
Fair 62.1% (77)
Poor 6.5% (8)
St. Mary County's Poor-condition bridges carry 55,494 vehicle crossings a day
That is 7.1% of the county's reported daily bridge traffic on 6.5% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 6,937 crossings a day against 9,175 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 124 of 124 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
38.7% of St. Mary County's bridges have passed the 50-year mark
48 of the 124 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 31.5% 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 23% of the county's Poor-condition bridge traffic
LA0182 over ATCHAF.R/BERWICK BAY, built 1933, carries 12,788 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 8-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 55,494 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When St. Mary County's bridges were built
124 bridges with a recorded construction year, grouped by decade
- 1930s 5
1930–1939
5 bridges
- 1940s 2
1940–1949
2 bridges
- 1950s 11
1950–1959
11 bridges
- 1960s
1960–1969
23 bridges
- 1970s
1970–1979
43 bridges
- 1980s
1980–1989
21 bridges
- 1990s 11
1990–1999
11 bridges
- 2000s 4
2000–2009
4 bridges
- 2010s 3
2010–2019
3 bridges
- 2020s 1
2020–2029
1 bridges
What this shows Construction peaked in the 1970s, when 43 of the county's bridges still in the inventory were built, which is 34.7% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1975, 7 years older than the Louisiana average of 1982.
How St. Mary County compares with Louisiana's closest counties by inventory size
The 5 Louisiana counties nearest St. Mary County in number of bridges, with their condition splits. Its 6.5% Poor share is the 2nd-lowest of these 6. Its average build year of 1975 against a peer-group mean of 1982 is 7 years older.
Showing the 5 closest of 63 Louisiana counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Franklin County | 131 | 64.9% | 32.1% | 3.1% | 1989 |
| Lafourche County | 130 | 39.2% | 44.6% | 16.2% | 1981 |
| Caldwell County | 124 | 57.3% | 34.7% | 8.1% | 1982 |
| St. Mary County (this page) | 124 | 31.5% | 62.1% | 6.5% | 1975 |
| Union County | 121 | 21.5% | 66.9% | 11.6% | 1977 |
| St. Martin County | 116 | 37.9% | 53.4% | 8.6% | 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 St. Mary 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 St. Mary County, both outside Louisiana so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside LA (124 bridges here).
- Bannock County, ID · 124 bridges
- Breathitt County, KY · 124 bridges
- Bollinger County, MO · 124 bridges
- Park County, MT · 124 bridges
Similar average build year
Nearest mean year-built outside LA (1975 here).
- San Bernardino County, CA · avg 1975 · 1,422 bridges
- Lane County, OR · avg 1975 · 1,010 bridges
- Fulton County, GA · avg 1975 · 775 bridges
- Westmoreland County, PA · avg 1975 · 620 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Good-condition bridges (39)
Willow St.
GoodOver: COULEE
1.2 Mi. W of LA 182, St. Mary, LA
Built 1957 Load: 17.2 t ADT: 1,350
LA0083
GoodOver: KELLY CANAL
2.80 MI WEST OF US 90, St. Mary, LA
Built 1954 Load: 24.0 t ADT: 3,078
US0090
GoodOver: CREEK
1.4 Mi W of La 662, St. Mary, LA
Built 1998 Load: 28.2 t ADT: 10,035
US0090
GoodOver: CREEK
6.24 Mi E of LA 182, St. Mary, LA
Built 1998 Load: 29.2 t ADT: 4,014
US0090
GoodOver: WEST APPR ATCHAFALAYA R
0.2 MI SE OF LA 182, St. Mary, LA
Built 1977 Load: 29.9 t ADT: 7,885
US0090
GoodOver: RAMP M
6.3 MI W OF LA 662, St. Mary, LA
Built 1984 Load: 29.9 t ADT: 24,384
PARISH ROUTE 18
GoodOver: CHARENTON FLOODGATE
CHARENTON LEVEE, St. Mary, LA
Built 1951 Load: 31.4 t ADT: 100
US0090/SERVICE RD
GoodOver: COULEE
0.9 MI WEST OF LA 182, St. Mary, LA
Built 1975 Load: 31.8 t ADT: 162
LA0083
GoodOver: CREEK
2.9 Mi. East of LA 318, St. Mary, LA
Built 1954 Load: 32.4 t ADT: 1,382
LA0083
GoodOver: LITTLE BAYOU BLACK
0.6 MI NORTH OF LA 319, St. Mary, LA
Built 1960 Load: 32.4 t ADT: 3,078
US0090
GoodOver: CREEK
1.2 MI EAST OF LA 182, St. Mary, LA
Built 1964 Load: 32.4 t ADT: 9,896
US0090
GoodOver: LA 83 S.P. RR
3.2 MI NW OF LA 3211, St. Mary, LA
Built 1978 Load: 32.7 t ADT: 10,070
US0090
GoodOver: ON-RAMP
0.14 MI W of LA 182, St. Mary, LA
Built 1977 Load: 32.7 t ADT: 7,885
US0090
GoodOver: US 90 EB ON RAMP
0.14 MI W of LA 182, St. Mary, LA
Built 1977 Load: 32.7 t ADT: 10,035
US0090
GoodOver: 6th
1.4 MI W of LA 182/LA 70, St. Mary, LA
Built 1977 Load: 32.7 t ADT: 2,163
US0090
GoodOver: RAMP J
0.09 MI E of LA 182, St. Mary, LA
Built 1984 Load: 32.7 t ADT: 12,192
US0090
GoodOver: RAMP I
0.17 MI E of LA 182, St. Mary, LA
Built 1984 Load: 32.7 t ADT: 24,384
US0090/Ramp C
GoodOver: 6th St.
8.9 MI EAST OF LA 182, St. Mary, LA
Built 1977 Load: 33.6 t ADT: 12,192
US0090
GoodOver: RAMP G
0.02 MI SW OF LA 182, St. Mary, LA
Built 1977 Load: 33.6 t ADT: 12,192
US0090-W
GoodOver: SOUTHERN PACIFIC RAILROA
2.5 MI EAST OF US90, St. Mary, LA
Built 1997 Load: 34.5 t ADT: 12,788
US0090
GoodOver: RAMP K
0.9 MI E of LA 182, St. Mary, LA
Built 1984 Load: 35.4 t ADT: 12,192
US0090
GoodOver: RAMP L
0.9 MI E of LA 182, St. Mary, LA
Built 1984 Load: 35.4 t ADT: 12,192
US0090
GoodOver: LA 83 S.P. RR
4.6 MI E OF LA 318, St. Mary, LA
Built 1978 Load: 37.2 t ADT: 16,253
US0090
GoodOver: 7th Street
1.34 Mi. E. of 182 US 90, St. Mary, LA
Built 1977 Load: 37.2 t ADT: 12,192
LA0323
GoodOver: Bayou Teche
0.2 Mi W. of LA 87, St. Mary, LA
Built 2022 Load: 38.2 t ADT: 170
LA0182
GoodOver: YOKELY BAYOU
0.26 MI S of LA 3211, St. Mary, LA
Built 2001 Load: 39.0 t ADT: 6,242
US0090
GoodOver: WAX LAKE OUTLET
0.6 MI EAST OF LA 182, St. Mary, LA
Built 1995 Load: 39.0 t ADT: 7,885
US0090
GoodOver: RAMP N
0.05 MI E OF DR. MLK BLVD, St. Mary, LA
Built 1984 Load: 39.0 t ADT: 12,192
US0090
GoodOver: CHARENTON CANAL
2.05 MI W of LA 3211, St. Mary, LA
Built 1978 Load: 40.8 t ADT: 21,000
US0090
GoodOver: VACHERIE CANAL
1.4 MI EAST OF LA 318, St. Mary, LA
Built 1978 Load: 43.5 t ADT: 269
Thorguson Dr.
GoodOver: SIMMONS BAYOU
0.7 Mi S of US 90, St. Mary, LA
Built 2013 Load: 43.7 t ADT: 1,200
US0090
GoodOver: LA 318
4.6 MI W OF LA 83, St. Mary, LA
Built 2017 Load: 46.0 t ADT: 10,080
US0090
GoodOver: LA 318
3.1 MI E OF LA 668, St. Mary, LA
Built 2017 Load: 46.0 t ADT: 8,073
US0090
GoodOver: TEXAS GAS PIPELINE
6.4 Mi E of LA 182, St. Mary, LA
Built 1994 Load: 46.3 t ADT: 7,885
US0090
GoodOver: TEXAS GAS PIPELINE
2.27 Mi W of LA 662, St. Mary, LA
Built 1994 Load: 46.3 t ADT: 10,035
US0090
GoodOver: PATTERSON CANAL
2.6 MI EAST OF LA 182, St. Mary, LA
Built 1964 Load: 66.4 t ADT: 22,893
US0090
GoodOver: CREEK
2.0 MI EAST OF LA 182, St. Mary, LA
Built 1964 Load: 74.5 t ADT: 9,896
US0090
GoodOver: CREEK
2.1 MI EAST OF LA 182, St. Mary, LA
Built 1964 Load: 74.5 t ADT: 7,885
US0090
GoodOver: CREEK
2.1 MI EAST OF LA 182, St. Mary, LA
Built 1964 Load: 74.5 t ADT: 10,035
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.