Longest Bridges in Montana

The longest bridge in Montana spans 2437.0 feet. The table below ranks the state's bridges by total structure length — from major river crossings and causeway spans to long highway overpasses.

How this ranking works

Length comes from the NBI structure length field and is shown in feet. It is best read as a scale and maintenance-complexity signal, not by itself as a safety signal.

Bridge	County	Length	Condition	Year Built
Koocanusa Bridge over Koocanusa Reservoir	Lincoln	2437.0 ft	Fair	1971
US 87-mt 3-mt 200 over Missouri River-u5205-rr	Cascade	2121.4 ft	Fair	1983
US 89-mt 3-mt 200 over Missouri River-u5205-rr	Cascade	2092.2 ft	Fair	1951
I 94 over Yellowstone River	Dawson	2013.8 ft	Fair	1968
I 94 over Yellowstone River	Dawson	1973.8 ft	Fair	1968
Bbp over Yellowstone River	Yellowstone	1858.9 ft	Good	2022
Montana AVE over U1024-25-rr	Yellowstone	1712.9 ft	Poor	1960
Montana AVE over U1025-rr	Yellowstone	1710.6 ft	Poor	1960
IRR - US 93 over Flathead River	Lake	1536.7 ft	Fair	1966
IRR - US 2 over Two Medicine River	Glacier	1521.0 ft	Fair	2012
S 200s-towne ST over Yellowstone River	Dawson	1322.5 ft	Fair	1958
I 15 over Missouri Rvr-rr-local	Lewis and Clark	1287.7 ft	Fair	1971
I 90 EB over Clark Fork Rvr-local RD	Mineral	1282.8 ft	Fair	1982
I 15 over Missouri Rvr-rr-local	Lewis and Clark	1249.7 ft	Fair	1971
S 37 Fh 57 over Kootenai River	Lincoln	1236.9 ft	Fair	1969
9th ST N over Missouri River	Cascade	1232.3 ft	Fair	1996
I 94 over Yellowstone River	Prairie	1169.3 ft	Fair	1978
I 94 over Yellowstone River	Prairie	1169.3 ft	Fair	1978
I 90 WB over Clark Fork Rvr-local RD	Mineral	1144.7 ft	Fair	1984
Frontage Road 114 over Yellowstone River 015	Prairie	1144.7 ft	Fair	1945
15th ST N-us 87 over Missouri R-rivers Trail	Cascade	1125.7 ft	Fair	1962
S 200 over Clark Fork River	Sanders	1109.6 ft	Fair	1997
S 23 over Yellowstone River	Richland	1102.0 ft	Poor	1994
I 90 over Clark Fork River	Mineral	1091.9 ft	Fair	1982
I 90 over Clark Fork River	Mineral	1091.9 ft	Poor	1984
York RD over Missouri River	Lewis and Clark	1079.7 ft	Fair	1982
Milwaukee RD over Yellowstone River 030	Prairie	1077.8 ft	Fair	1907
Tusler RD over Yellowstone River 094	Custer	1064.0 ft	Fair	1907
S 200 over Clark Fork River	Sanders	1061.0 ft	Fair	1958
IRR - SR 480 over Missouri River	Richland	1056.8 ft	Fair	1968
Scott ST over Rr	Missoula	1024.3 ft	Fair	1979
Old HWY 312 over Yellowstone River 170	Yellowstone	1022.0 ft	Poor	1949
I 90 over Clark Fork River	Missoula	1019.7 ft	Fair	1979
State Highway 24 over Ft. Peck Spillway	McCone	1017.7 ft	Fair	1937
I 90 over Clark Fork River	Missoula	981.6 ft	Poor	1964
5th AVE S over Clark Fork 085	Sanders	979.7 ft	Fair	1975
S 59 over Yellowstone River	Custer	976.0 ft	Fair	1957
I 90 over Yellowstone River	Yellowstone	975.1 ft	Fair	2022
I-90 over Yellowstone River	Yellowstone	975.1 ft	Fair	2023
S Higgins AVE over Clark Fork R-ped Paths	Missoula	973.8 ft	Fair	1962
Central AVE over Missouri River-ped Trail	Cascade	963.9 ft	Good	1980
S 16 over Missouri River	Richland	954.7 ft	Fair	1988
S 200 over Clark Fork River	Sanders	952.4 ft	Poor	1960
US 2 over Kootenai River-rr	Lincoln	941.9 ft	Poor	1942
Pn Bridge RD over Missouri River	Chouteau	903.9 ft	Fair	1982
I 90 over Clark Fork Rvr-rr-local	Mineral	901.9 ft	Fair	1982
S 253 over Yellowstone River	Prairie	896.3 ft	Fair	1959
S 35 over Flathead River	Flathead	883.9 ft	Fair	1994
I 90 over Clark Fork Rvr-rr-local	Mineral	880.6 ft	Fair	1982
I 90 over Clark Fork River	Missoula	878.9 ft	Fair	1964
I 90 over Clark Fork River	Mineral	866.8 ft	Fair	1981
S Billings BLVD over Yellowstone River	Yellowstone	860.9 ft	Fair	1972
I 15 over Int Dearborn-missouri R	Cascade	849.7 ft	Fair	1971
IRR - US 2 over S Fork Flathead River	Flathead	843.5 ft	Good	2018
I 15 over Int Dearborn-missouri R	Cascade	840.9 ft	Fair	1971
N Reserve ST over Clark Fork River	Missoula	831.7 ft	Fair	1975
US 12 over Yellowstone River	Rosebud	829.7 ft	Fair	1958
7th AVE N over Rr	Hill	827.8 ft	Fair	1936
I 90 over Clark Fork River	Mineral	825.8 ft	Fair	1967
I 90 over Clark Fork River	Mineral	825.8 ft	Fair	1967
I 15 over Missouri River-local	Cascade	818.9 ft	Fair	1971
I 90 over Clark Fork River	Mineral	806.8 ft	Poor	1965
Bundy RD over Yellowstone River	Yellowstone	805.1 ft	Fair	2001
I 90 over Clark Fork River	Mineral	800.9 ft	Fair	1966
I 90 over Clark Fork River	Mineral	800.9 ft	Fair	1960
I 15 over Missouri River-local	Cascade	791.7 ft	Fair	1971
I 15 over Sep Boulder Ave-rr	Lewis and Clark	791.0 ft	Fair	2016
I 94 over Int Circle-rr-7m CR	Dawson	788.7 ft	Fair	1969
Old HWY 10 E over Clark Fk-rr 060	Mineral	786.7 ft	Fair	1942
I 15 over Sep Boulder Ave-rr	Lewis and Clark	784.1 ft	Fair	2017
I 90 over Int Cyr-clark Fork Rvr	Mineral	780.8 ft	Fair	1981
I 94 over Int Circle-rr-7m CR	Dawson	772.6 ft	Fair	1969
I 15 over Sep Missouri Rvr-co RD	Lewis and Clark	770.7 ft	Fair	1967
I 15 over Sep Missouri Rvr-co RD	Lewis and Clark	770.7 ft	Fair	1967
Heron RD over Cabinet Gorge Res 049	Sanders	767.4 ft	Good	2017
I 90 over Int Cyr-clark Fork Rvr	Mineral	761.8 ft	Fair	1965
I 90 over Clark Fork River	Mineral	756.9 ft	Fair	1967
I 90 over Clark Fork River	Mineral	756.9 ft	Fair	1967
US 12 over Little Blackfoot Riv-rr	Powell	745.1 ft	Fair	2009
I 15 over Rr-missouri River	Cascade	740.5 ft	Fair	1968
I 15 over Rr-missouri River	Cascade	738.8 ft	Fair	1968
I 90 over Madison River-rr	Gallatin	735.9 ft	Fair	1964
I 90 over Yellowstone River	Park	730.0 ft	Fair	1962
I 90 over Yellowstone River	Park	730.0 ft	Fair	1962
Conrad DR over Flathead River 013	Flathead	726.0 ft	Fair	2009
Kona Ranch RD over Clark Fork 011	Missoula	724.7 ft	Fair	1987
I 90 over Int W Garrison-rr	Powell	709.6 ft	Poor	1979
I 90 over Int W Garrisison-rr	Powell	709.6 ft	Fair	1979
S 80-13th ST over Missouri River	Chouteau	708.0 ft	Poor	1962
Myers RD over Yellowstone River	Treasure	705.7 ft	Fair	1968
US 191 over Missouri River	Fergus	697.8 ft	Poor	1959
California AVE over Kootenai River	Lincoln	697.8 ft	Fair	1959
S 82 over Flathead River	Flathead	685.7 ft	Poor	1955
S 446 over Yellowstone River	Rosebud	683.1 ft	Fair	1970
Mt 37 Fh 57 over Sutton Creek	Lincoln	661.7 ft	Fair	1974
US 287 over Missouri River	Broadwater	661.1 ft	Good	2020
IRR - S 382 over Flathead River	Sanders	653.5 ft	Fair	1965
Central AVE E over Missouri River	Cascade	652.9 ft	Fair	1954
I 15 over Little Prickly Pear CR	Lewis and Clark	652.2 ft	Fair	1965
Business RTE 90 over Yellowstone River	Park	641.7 ft	Fair	2013
I 90 over St. Regis Rvr-local RD	Mineral	637.8 ft	Fair	1979
Old HWY 10 W over Powder River 040	Prairie	635.8 ft	Fair	1945
Old HWY 10 over Bighorn River 126	Yellowstone	629.3 ft	Fair	1930
IRR - S 13 over Missouri River	Roosevelt	625.7 ft	Fair	1998
US 212 over Powder River	Powder River	625.0 ft	Good	1985
I 90 over Madison River-rr	Gallatin	624.7 ft	Fair	1964
IRR - US 2 over Middle Fork Flathead Riv	Flathead	623.4 ft	Fair	2002
US 12 over Powder River	Custer	622.0 ft	Fair	1973
I 90 over Clark Fork River	Mineral	620.7 ft	Fair	1960
I 15 over Local-creek-rarus Rr	Silver Bow	613.2 ft	Fair	1961
Noxon AVE E over Cabinet Gorge Resv 047	Sanders	599.7 ft	Poor	1922
I 15 over Local-creek-rarus Rr	Silver Bow	598.4 ft	Fair	1961
I 15 over Silverbow Creek-rr	Silver Bow	598.1 ft	Good	2018
I 15 over Silverbow Creek-rr	Silver Bow	598.1 ft	Good	2019
I 90 over Int E Garrison-rr	Powell	597.8 ft	Fair	1979
IRR - I 90 over Bighorn River	Big Horn	593.5 ft	Good	1971
IRR - I 90 over Bighorn River	Big Horn	593.5 ft	Fair	1971
I 90 Frontage RD over Bighorn River	Big Horn	590.6 ft	Fair	2007
I 90 over Int E Garrison-rr	Powell	581.7 ft	Fair	1979
I 94 over Bighorn River	Yellowstone	580.1 ft	Fair	1963
I 90 over Yellowstone River	Stillwater	577.8 ft	Fair	1976
IRR - S 313 over Bighorn River	Big Horn	575.8 ft	Fair	1958
S 78 over Yellowstone River	Stillwater	575.8 ft	Poor	1957
I 15 over Rr-hwy 91- Drainage	Madison	570.9 ft	Fair	1974
I 94 over Bighorn River	Yellowstone	570.5 ft	Fair	1978
Musselshell Trl RD over Yellowstone River	Yellowstone	566.9 ft	Fair	1964
US 87 over Yellowstone River	Yellowstone	565.9 ft	Fair	1993
I 15 over Sep Rr	Beaverhead	560.4 ft	Fair	2016
I 90 over Yellowstone River	Stillwater	557.7 ft	Fair	1961
Duck Creek RD over Yellowstone River 020	Yellowstone	557.7 ft	Fair	1991
I 90 over Int W Laurel-rr	Yellowstone	556.1 ft	Fair	2018
Central AVE W over Galt Ave-rr	Cascade	553.1 ft	Fair	1967
Madison St-us 12 over Clark Fork River	Missoula	551.8 ft	Fair	1958
US 93 over Bitterroot River	Ravalli	551.8 ft	Fair	2005
Old US 91 over Missouri River-rr 069	Cascade	549.9 ft	Poor	1931
I 90 over Clark Fork River	Mineral	544.9 ft	Fair	1976
Marias Valley RD over Marias River 001	Toole	544.9 ft	Fair	1936
I 15 over Int Spring Creek-rr	Lewis and Clark	539.4 ft	Fair	1964
I 94 over Powder River	Prairie	539.4 ft	Fair	1971
Central AVE W over Galt Ave-rr	Cascade	538.1 ft	Fair	1967
I 15 over Rr-hwy 91-drainage	Madison	538.1 ft	Fair	1974
I 94 over Powder River	Prairie	538.1 ft	Fair	1971
I 15 over Missouri River	Cascade	532.8 ft	Fair	1971
I 15 over Missouri River	Cascade	532.8 ft	Fair	1971
HWY 287 Bypass over Missouri River 019	Broadwater	531.8 ft	Poor	1920
Millegan RD over Missouri River	Cascade	530.2 ft	Fair	1983
I 15 over Int Spring Creek-rr	Lewis and Clark	529.9 ft	Fair	1964
US 87 over Abandoned Railroad	Chouteau	527.9 ft	Fair	1974
Buffalo Bridge RD over Flathead River 084	Lake	527.9 ft	Fair	1993
I 15 over Little Prickly Pear CR	Lewis and Clark	525.9 ft	Fair	1965
IRR BIA RTE 91 over Big Horn River	Big Horn	524.9 ft	Fair	1970
Old HWY 10 W over Clark Fork 054	Mineral	518.0 ft	Poor	1932
US 212 over Yellowstone River	Yellowstone	512.8 ft	Good	1997
Craig Frontage RD over Missouri River 054	Lewis and Clark	506.9 ft	Poor	1933
6th ST SW over Sun River	Cascade	505.9 ft	Fair	1980
Reed Point RD over Yellowstone River 004	Stillwater	505.2 ft	Fair	2000
I 94 over Rr	Prairie	501.6 ft	Fair	1969
US 12 over Missouri River	Broadwater	500.0 ft	Fair	1935
S Orange ST over Clark Fork River	Missoula	496.7 ft	Fair	2003
IRR - S 200 over Jocko River-rr	Lake	493.4 ft	Fair	1998
Rapelje RD over Sep Rapelje-i 90	Stillwater	492.8 ft	Fair	1971
Bridge ST over Missouri River 062	Lewis and Clark	490.5 ft	Good	2006
Reserve ST over W Broadway St-rr	Missoula	489.8 ft	Fair	1998
David Thompson Brg over Kootenai River D/s Dam	Lincoln	488.8 ft	Fair	1967
IRR - US 2 over Flathead River	Flathead	488.5 ft	Fair	1977
I 90 over Blackfoot River	Missoula	486.2 ft	Good	2018
I 15 NB over Sun River	Cascade	484.9 ft	Fair	1966
I 15 SB over Sun River	Cascade	484.9 ft	Fair	1966
I 15 over Marias River	Toole	483.9 ft	Good	1976
I 15 over Marias River	Toole	483.9 ft	Good	1976
Sloway Frntge RD E over Abandoned Rr 001	Mineral	482.0 ft	Poor	1956
I 15 over Sep Rr	Beaverhead	481.0 ft	Fair	1980
I 94 over Rr-highline Canal RD	Yellowstone	480.0 ft	Fair	1968
S 213 over Rr	Glacier	474.7 ft	Good	2012
I 90 over Int W Laurel-rr	Yellowstone	473.1 ft	Good	2019
Old Stage Road over Yellowstone River 077	Park	471.8 ft	Fair	1980
RD 552 over Powder River 016	Powder River	470.5 ft	Fair	2008
S 200 over Clark Fork River	Sanders	469.8 ft	Fair	1996
I 90 over Black Foot River	Missoula	468.2 ft	Good	2019
Lozeau Crossovr RD over Clark Fork 045	Mineral	463.9 ft	Fair	1944
No Data Entered over Nezperce Fk	Ravalli	463.9 ft	Fair	1972
N Russel Street over Clark Fork River	Missoula	463.6 ft	Good	2020
S 41 over Jefferson River	Madison	462.3 ft	Fair	1992
Petty Creek RD over Clark Fork 008	Missoula	457.0 ft	Fair	1964
S Shiloh RD over Sep I 90	Yellowstone	457.0 ft	Poor	1959
Trail Creek RD over Powder River 061	Custer	455.1 ft	Fair	1926
I 90 over St. Regis Rvr-local RD	Mineral	455.1 ft	Fair	1979
I 90 over Clark Fork River	Missoula	455.1 ft	Fair	1965
I 90 over Clark Fork River	Missoula	455.1 ft	Fair	1965
F Bridge RD over Marias River	Toole	455.1 ft	Fair	1953
I 15 over Big Hole River	Madison	452.8 ft	Fair	1973
Rock CR RD over Clark Fk-rr-hwy 106	Missoula	450.1 ft	Fair	1972
US 89 over Yellowstone River	Park	450.1 ft	Fair	1958
S 200 over Blackfoot River	Missoula	449.8 ft	Fair	1968
I 15 over Beaverhd R-high Brdg RD	Beaverhead	448.2 ft	Fair	1981
I 90 over Sep Elizabeth LN	Mineral	447.8 ft	Good	1981
I 94 over Rr-highline Canal RD	Yellowstone	446.9 ft	Fair	1968
I 90 over Sep Elizabeth LN	Mineral	445.9 ft	Poor	1965
S 200 EB over Blackfoot River	Missoula	445.9 ft	Fair	1940
S 200 over Blackfoot River	Missoula	445.9 ft	Fair	1988