McKinney Creek Bridge (Polk County, Arkansas)
Built 1915
Pony truss bridge over McKinney Creek on CR 50
Open to one-lane traffic

McLean Branch MO 79 Bridge (Lincoln County, Missouri)
Built 1938
Through truss bridge over McLean Branch on MO 79 at Winfield
Open to traffic

McNeely Creek Bridge (Clark County, Arkansas)
Built 1923; rehabilitated 1990
Pony truss bridge over McNeely Creek on CR 12
Open to one-lane traffic

Mechanicsville Covered Bridge (Ashtabula County, Ohio)
Built 1867; rehabilitated 2003
Covered bridge over Grand River on Windsor-Mechanicsville Road
Open to traffic

Meeker Drive Bridge (Cowlitz County, Washington)
Built 1952
Truss bridge over Kalama River on Meeker Drive
Open to traffic

Melcher Covered Bridge (Parke County, Indiana)
Built 1896 by J.J. Daniels; rehabilitated 1977 and 1995
Covered bridge over Leatherwood Creek on CR W20N
Open to traffic

Memorial Drive Bridge (Racine County, Wisconsin)
Built 1936
Concrete arch bridge over Root River on Memorial Drive in Racine
Open to traffic

Memphis-Arkansas Bridge (Shelby County, Tennessee)
Built 1949
Cantilevered through truss bridge over the Mississippi River on I-55 at Memphis
Open to four lanes of traffic

Mengo Bridge (Butler County, Missouri)
Built 1906 by the American Bridge Co.
Two-span through truss bridge over Black River on the Union Pacific Railroad, between Poplar Bluff and Hilliard
Still in use

Meramec River MO 21 Bridge (St. Louis County, Missouri)
Built 1940
Steel through arch bridge over the Meramec River on MO 21
Open to four lanes of traffic

Meramec River US 66 Bridge (St. Louis County, Missouri)
Built 1931
Deck truss bridge over Meramec River at Times Beach on Old US 66 in Wildwood
Open to traffic on a frontage road within Route 66 State Park

Merchants Bridge (St. Louis, Missouri)
Completed May 1890
Three-span through truss railroad bridge over the Mississippi River between St. Louis and Venice, Illinois
Open to railroad traffic only

Meridian Bridge (Sutter County, California)
Built 1977
Swing bridge over Sacramento Riv(Meridian) on CA 20
Open to traffic

Meridian Bridge (Yankton County, South Dakota)
Built 1924; rehabilitated 1953
Vertical-lift through truss bridge over the Missouri River on US 81 at Yankton
Open to traffic

Merriam Street Bridge (Hennepin County, Minnesota)
Originally built 1887 by the King Iron Bridge Co. as a four-span truss bridge on Broadway Street; one span relocated here in 1987
Relocated through truss bridge over the Mississippi River (East Channel) on Merriam Street at Nicollet Island in Minneapolis
Open to traffic

Messmer Street Bridge (Scott County, Missouri)
Concrete bridge on Messmer Street (Old US 61) over a branch of Ramsey Creek just north of Kelso
Open to traffic

Metropolis Bridge (Massac County, Illinois)
Built 1917 under the direction of engineers C. H. Cartlidge and Ralph Modjeski
Six-span through truss bridge over the Ohio River on the CN Railroad at Metropolis
Open to railroad traffic

Miami Bridge (Saline County, Missouri)
Built 1939; rehabilitated 1983
Cantilevered through truss bridge over the Missouri River on MO 41 at Miami
Open to traffic

Miami Creek CR 181 Bridge (Bates County, Missouri)
Built 1925
Pony truss bridge over Miami Creek on CR 181 (Elkhart Road)
Open to traffic

Michigan Avenue Bridge (Cook County, Illinois)
Built 1920
Bascule bridge over Main Branch Chicago River on Michigan Avenue in Chicago
Open to traffic

Michigan Street Bridge (Milwaukee County, Wisconsin)
Built 1978
Vertical lift bridge over Milwaukee River on Michigan Street in Milwaukee
Open to traffic

Middle Beaver Creek Lincoln Highway Bridge (Greene County, Iowa)
Built 1915
Stringer bridge over Middle Beaver Creek on 210th Avenue, Original Lincoln Highway
Open to traffic

Middle Creek Bridge (Miami County, Kansas)
Built ca. 1920
Concrete arch bridge over Middle Creek, 9.0 mi. south and 3.6 mi. west of Louisburg
Open to traffic

Middle Creek Bridge (Miami County, Kansas)
Built 1907
Through truss bridge over Middle Creek on 379th Street, 1.5 mi. south and 1.8 mi. west of New Lancaster
Open to traffic

Middle Creek Bridge (Miami County, Kansas)
Pony truss bridge over Middle Creek, 1.3 mi. south and 1.0 mi. west of Beagle
Open to traffic

Middle Creek Bridge (Miami County, Kansas)
Built 1914 by the Topeka Bridge & Iron Co.
Concrete arch bridge over Jake's Branch of Middle Creek on 335th Street, 7.0 mi. south and 2.1 mi. west of Louisburg
Open to traffic

Middle Fork AR 7 Bridge (Garland County, Arkansas)
Built 1933 by the Ault-Rich Construction Co. of Cassville, Missouri
Two-span open-spandrel arch bridge over Middle Fork Saline River on AR 7
Open to two-lane traffic

Middle Fork Smith River Bridge (Del Norte County, California)
Built 1925; rehabilitated 1972
Concrete arch bridge over Middle Fork Smith River on US 199
Open to traffic

Middle River Bridge (Madison County, Iowa)
Built 1932
Through truss bridge over Middle River on a local road
Open to traffic

Middle River Route 774 Bridge (Augusta County, Virginia)
Built 1903
Through truss bridge over Middle River on Route 774
Open to one-lane traffic

Middle River Route 775 Bridge (Augusta County, Virginia)
Built 1908
Through truss bridge over Middle River on Route 775
Open to traffic

Middle River Route 778 Bridge (Augusta County, Virginia)
Built 1915 by the Champion Bridge Co.
Through truss bridge over Middle River on Route 778
Open to traffic

Middle Road Covered Bridge (Ashtabula County, Ohio)
Built 1868; rehabilitated 1984
Covered bridge over Conneaut Creek on Middle Road in Conneaut
Open to traffic

Middlebury Street Bridge (Elkhart County, Indiana)
Built 1931 by Bontrager Construction Co.; rehabilitated 1985
Three-span concrete arch bridge over Elkhart River on Middlebury Street in Elkhart
Open to traffic

Midland Fredericktown Road Bridge (Columbiana County, Ohio)
Built 1900; rehabilitated 2004
Through truss bridge over North Fork Little Beaver Creek on Midland Fredericktown Road (TR 1038) in Calcutta
Open to traffic

Midland Tunnel No. 1 (Chaffee County, Colorado)
Built 1887 by the Colorado Midland Railroad
First of four tunnels on CR 371 north of Buena Vista
Open to one-lane traffic

Midland Tunnel No. 2 (Chaffee County, Colorado)
Built 1887 by the Colorado Midland Railroad
Second of four tunnels on CR 371 north of Buena Vista
Open to one-lane traffic

Midland Tunnel No. 3 (Chaffee County, Colorado)
Built 1887 by the Colorado Midland Railroad
Third of four tunnels on CR 371 north of Buena Vista
Open to one-lane traffic

Midland Tunnel No. 4 (Chaffee County, Colorado)
Built 1887 by the Colorado Midland Railroad
Fourth of four tunnels on CR 371 north of Buena Vista
Open to one-lane traffic

Milk River Bridge (Blaine County, Montana)
Built 1916
Timber through truss bridge over Milk River on CR 178
Open to traffic

Mill Creek Bridge (Bourbon County, Kansas)
Built 1927
Through arch bridge over Mill Creek on North Crawford in Fort Scott
Open to traffic

Mill Creek Bridge (Wasco County, Oregon)
Built 1948
Deck truss bridge over Mill Creek on US 26
Open to traffic

Mill Creek Bridge (Washington County, Missouri)
Built 1935
Concrete tee beam bridge over Mill Creek on Route M
Open to traffic

Mill Creek Bridge (Crawford County, Indiana)
Built 1885; rehabilitated 2000
Through truss bridge over Mill Creek on CR 220 East
Open to traffic

Mill Creek Bridge (Wabaunsee County, Kansas)
Deck plate girder bridge over Mill Creek on Southern Pacific Railroad
Open to traffic

Mill Creek Bridge (Wabaunsee County, Kansas)
Built ca. 1935
Through truss bridge over Mill Creek on Willard Road, 1.0 mi. east and 0.2 mi. north of Maple Hill
Open to traffic

Mill Creek Bridge Highway M (Washington County, Missouri)
Bridge over Mill Creek on Route M
Open to traffic

Mill Creek Covered Bridge (Parke County, Indiana)
Built 1907 by D.M. Brown
Covered bridge over Mill Creek on CR N550W
Open to traffic

Mill Creek MO 47 (Washington County, Missouri)
Built 1964
Steel stringer bridge over Mill Creek on Mo 47 S
Open to traffic

Mill Creek Park Suspension Bridge (Mahoning County, Ohio)
Built 1895 by the Youngstown Bridge Co.
Suspension bridge over Mill Creek in Mill Creek Park at Youngstown
Open to traffic

Mill Creek Swinging Bridge (Miller County, Missouri)
Built by Joseph Dice; rehabilitated 1978
Swinging bridge over Mill Creek on Lake Road 42-18 (Swinging Bridges Road) near Brumley
Open to one-lane traffic

Mill Road Bridge (Darke County, Ohio)
Built 1881 by the Massillon Bridge Co.
Through truss bridge over Greenville Creek on TR 385 in Gettysburg
Open to traffic

Millard Crossing Bridge (Logan County, Arkansas)
This bridge crosses Shoal Creek on north east side of Magazine mountain at the former town of Millard
Timber stringer bridge over Shoal Creek on Forest Service road #1601
Open to traffic

Miller Creek Bridge (Alexander County, Illinois)
Built 1933
Pony truss bridge over Miller Creek on Old Illinois Route 3 northeast of Thebes, 1 mi. north of Thebes
Open to two-lane traffic

Miller Creek Bridge (Independence County, Arkansas)
Built 1914
Two-span arch bridge over Miller Creek on Miller Creek Road (CR 86) in Batesville
Open to one-lane traffic

Miller Creek Stone Bridge (Wayne County, Missouri)
Built ca. 1930
Low-water bridge with stone masonry foundations on CR 417 over Miller Creek beyond the end of Route JJ
Open to traffic with a 4 ton weight limit

Millers Bridge (Butler County, Missouri)
Built 1924
Pony truss bridge over Cane Creek on Route PP (Old US 60) west of Poplar Bluff
Open to two-lane traffic

Millersville Bridge (Cape Girardeau County, Missouri)
Built 1923; rehabilitated 1975
Two-span through truss bridge over Whitewater River on MO 72 at Millersville
Open to two-lane traffic on a paved road

Million Dollar Bridge (Valdez-Cordova Census Area, Alaska)
Built 1910 on the CR&NW Railroad; closed 1938; reopened as a highway bridge in 1958; fourth span collapsed in earthquake on March 27, 1964, collapsed span repaired 2005
Four-span through truss bridge over Copper River on Copper River Highway
Open to one-lane traffic

Milltown High Street Bridge (Warren County, Pennsylvania)
Built 1937; rehabilitated 1982
Pony truss bridge over Tionesta Creek on PA 2002 (High Street) in Milltown
Open to traffic

Milwaukee River Broadway St. Bridge (Milwaukee County, Wisconsin)
Built 1982
Bascule bridge over Milwaukee River on Broadway Street (WI 32) in Milwaukee
Open to traffic

Milwaukee River Parkway, Lincoln Park, North Branch (Milwaukee County, Wisconsin)
Built 1940
Bridge over North Branch Milwaukee River on Milwaukee River Parkway
Open to traffic

Milwaukee River Parkway, Lincoln Park, South Branch (Milwaukee County, Wisconsin)
Built 1940
Bridge over South Branch Milwaukee River on Milwaukee River Parkway
Open to traffic

Mine Creek Bridge (Linn County, Kansas)
Built 1914
Concrete arch bridge over Mine Creek, 8.8 mi. north and 3.4 mi. east of Prescott
Open to traffic

Mine Creek Bridge (Linn County, Kansas)
Built 1927
Rainbow arch bridge over Mine Creek on Ungeheuer Road (Old US 69), five miles north of Prescott
Open to traffic

Miner Street Bridge (Clear Creek County, Colorado)
Built 1902 by Kuyes and Work. Reconstructed 1990 (the trusses are no longer load-bearing).
Reconstructed pony truss bridge over Clear Creek on Miner Street in Idaho Springs
Open to traffic

Minerva Creek Bridge (Marshall County, Iowa)
Built 1912
Arch bridge over Minerva Creek on a local road
Open to traffic

Minerva Creek Bridge (Marshall County, Iowa)
Built 1919
Pony truss bridge over Minerva Creek on a local road
Open to traffic

Mingo Ditch Bridge (Stoddard County, Missouri)
Formerly a bridge on the Frisco Hoxie Branch railroad built in 1926 (?) and refurbished for vehicle use when the line was discontinued
Pony truss bridge over Mingo Ditch southwest of Puxico on CR 499
Open to one-lane traffic on a gravel road with a 17 ton weight limit

Mingo Ditch Route T Bridge (Stoddard County, Missouri)
Built 1955
Steel stringer bridge with wooden piers over Mingo Ditch on Route T
Open to two-lane traffic

Minneapolis Railroad Bridge (Ottawa County, Kansas)
Through truss bridge over Pipe Creek on the Kyle Railroad at Minneapolis
Open to traffic

Minnesota River Bridge (Blue Earth County, Minnesota)
Built 1954
Through truss bridge over Minnesota River on CR 42
Open to traffic

Minnow Slough Bridge (Crawford County, Illinois)
Built 1909
Steel stringer bridge over Minnow Slough on TR 163, 1 mi. east of Palestine
Open to traffic

Minnow Slough Bridge No. 2 (Crawford County, Illinois)
Built 1909; rehabilitated 1982
Steel stringer bridge over Minnow Slough on TR 169A, 1.5 mi. NE Palestine
Open to traffic

Minot Viaduct (Ward County, North Dakota)
Massive steel railroad trestle over the Coteau di Missouri Valley on the BNSF Railroad, west of Minot
Still in use

Mission Bridge over the Los Angeles River (Los Angeles County, California)
Built 1944; rehabilitated 1955
Concrete arch bridge over Los Angeles River on US 101 in Los Angeles
Open to traffic

Mississippi County Road 307 Bridge (Mississippi County, Missouri)
Built 1921
Pony truss on CR 307 (Old US 60) near Birds Point over a drainage ditch emptying into Brewer Lake in Wyatt
Open to traffic on a paved road with a 20 ton weight limit

Mississippi County Road 310 Bridge (Mississippi County, Missouri)
Built ca. 1922; relocated here 1966
Pony truss bridge over a drainage ditch on CR 310
Open to traffic

Mississippi County Road 314 Bridge (Mississippi County, Missouri)
Built 1922 as part of a bridge with at least two spans; relocated here in 1965
Pony truss bridge over Ditch 29 on CR 314, just off MO 77 south of Wyatt
Open to traffic

Mississippi County Road 319 Bridge (Mississippi County, Missouri)
Built 1922 as part of a bridge with at least two spans; relocated here 1965
Pony truss bridge over Ditch 29 on CR 319 just off MO 77
Open to traffic

Mississippi County Road 322 Bridge (Mississippi County, Missouri)
Built ca. 1922; relocated here 1966
Pony truss bridge over Spillway Ditch on CR 322 southeast of Charleston
Open to traffic on a gravel road

Mississippi County Road 325 Bridge (Mississippi County, Missouri)
Built 1922; relocated here in 1966
Pony truss bridge over Spillway Ditch on CR 325 southeast of Charleston
Open to traffic on a gravel road

Mississippi County Road 418 Bridge (Mississippi County, Missouri)
Built ca. 1922; relocated here 1970
Pony truss bridge over St. James Ditch on CR 418 west of MO 105
Open to traffic

Mississippi County Road 521 Bridge (Mississippi County, Missouri)
Built ca. 1922; relocated here 1965
Pony truss bridge on CR 521 over Wilkinson Drainage Ditch just west of MO 102
Open to traffic

Mississippi River Bridge (Grant County, Wisconsin)
Built 1982
Steel through arch bridge over Mississippi River on US 61/US 151
Open to traffic

Mississippi River I-40 Bridge (Shelby County, Tennessee)
Built 1973
Two-span steel through arch bridge over the Mississippi River on I-40 at Memphis
Open to traffic

Mississippi River US 61 Bridge (Dubuque County, Iowa)
Built 1982
Steel through arch bridge over the Mississippi River on US 61 and US 151
Open to traffic

Missouri River Bridge (Doniphan County, Kansas)
Pennsylvania through truss bridge over Missouri River on Union Pacific Railroad
Open to traffic

Missouri Street Bridge (Washington County, Missouri)
Pony truss bridge over Breton Creek on Missouri Street in Potosi, just south of the courthouse
Open to traffic

Mobridge Railroad Bridge (Walworth County, South Dakota)
Through truss bridge over Missouri River (Oahe Lake) on the BNSF Railroad between Mobridge and Wakpala
Open to traffic

Modrow Road Bridge (Cowlitz County, Washington)
Built 1958
Steel arch bridge over Kalama River on Modrow Road
Open to traffic

Moline Main Street Bridge (Elk County, Kansas)
Pony truss on North Main Street over Wildcat Creek in Moline
Open to one lane traffic on a paved street

Mollys Run Bridge (Jefferson County, Indiana)
Built 1905
Pony truss bridge over Mollys Run on Brooksburg Manville Road (CR 260N)
Open to one-lane traffic

Monett Business US 60 Bridge (Barry County, Missouri)
Built 1935
Through truss bridge over the railroad on Business US 60 east of Monett
Open to two-lane traffic

Moniteau Church Road Bridge (Moniteau County, Missouri)
Built ca. 1930
Pony truss bridge over Howard Creek on Moniteau Church Road southwest of Jamestown
Open to traffic

Moniteau Creek Road Bridge (Cole County, Missouri)
Built 1915; made obsolete by a new bridge on MO 179 in 1967
Through truss bridge over Moniteau Creek on Moniteau Creek Road (Old MO 179)
Open to traffic

Monroe Street Bridge (Cook County, Illinois)
Built 1919
Bascule bridge over South Branch Chicago River on W. Monroe Street in Chicago
Open to traffic

Montezuma Bridge (Parke County, Indiana)
Built 1949; rehabilitated 1987
Six-span through truss bridge over Wabash River on US 36 at Montezuma
Open to two-lane traffic

Montoursville Bridge (Lycoming County, Pennsylvania)
Built 1931; rehabilitated 1994
Three-span through truss bridge over Loyalsock Creek on PA 2014 in Montoursville
Open to traffic

Monument Road Bridge (Harris County, Georgia)
Built 1930
Truss bridge over Sand Creek on Monument Road
Open to traffic