Owned by state government

Madisonville Armory (Hopkins County, Kentucky)
Maghera Glass-Ormsby Hall (Jefferson County, Kentucky)
Magnolia Grove (Hale County, Alabama)
A historic Greek Revival mansion in Greensboro, Alabama.
Magruder Plots (Payne County, Oklahoma)
Mahoning Creek bridge (Armstrong County, Pennsylvania)
Concrete arch bridge over Mahoning Creek on Deanville Road
Maidstone State Park (Essex County, Vermont)
Main Building (Fayette County, West Virginia)
Main Building (Los Angeles County, California)
Main Building, Tempe Normal School (Maricopa County, Arizona)
Main Hall (Bon Homme County, South Dakota)
Main Hall (Hinds County, Mississippi)
Main Hall/La Crosse State Normal School (La Crosse County, Wisconsin)
An imposing red brick building that is the centerpiece of the UWL campus
Main Street Bridge (Fremont County, Colorado)
Concrete arch bridge over Coal Creek on CO 115 in Florence
Maine Experiment Station Barn (Penobscot County, Maine)
Maine Insane Hospital (Kennebec County, Maine)
Maine State House (Kennebec County, Maine)
Maitland Arroyo Bridge (Huerfano County, Colorado)
Wooden bridge over Maitland Arroyo on CO 69
Malabar Farm (Richland County, Ohio)
Malcolm Jeffrey House (Franklin County, Ohio)
Malone Armory (Franklin County, New York)
Mangum Armory (Greer County, Oklahoma)
Manhattan Bridge (Unspecified county, New York)
Suspension bridge over East River in New York City
Mansfield Armory (Tioga County, Pennsylvania)
Mansfield Battle Park (De Soto Parish, Louisiana)
Mansfield Training School and Hospital (Tolland County, Connecticut)
A state-run facility for the mentally retarded, closed since 1993.
Manship House (Hinds County, Mississippi)
Maplewood (Somerset County, New Jersey)
Marais des Cygnes Massacre Site (Linn County, Kansas)
Marble Springs (Knox County, Tennessee)
March Route of Rochambeau's Army: Palmer Road (Windham County, Connecticut)
Marconi Tower at Port Arthur College (Jefferson County, Texas)
Margots (Charles City County, Virginia)
Marine Air Terminal (Queens County, New York)
Marion Bridge (Unspecified county, Pennsylvania)
Lost cantilevered through truss bridge over the Monongahela River on PA 88
Marion Memorial Bridge (Marion County, Tennessee)
2 Parker Camelback through trusses, and 2 Warren through trusses with Polygonal top chords, all riveted, over Nickajack Lake (Tennessee River)
Mark Twain Birthplace Cabin (Monroe County, Missouri)
Market Street Bridge (Unspecified county, Pennsylvania)
Sixteen-span concrete arch bridge over East Channel Susquehanna River on Market Street (PA 3012) in Harrisburg
Market Street Bridge (Luzerne County, Pennsylvania)
Open-spandrel arch bridge over Susquehanna River on PA 1009 (Market Street) in Wilkes-Barre
Marks' Mills Battlefield Park (Cleveland County, Arkansas)
Marlow Armory (Stephens County, Oklahoma)
Maroon Creek Bridge (Pitkin County, Colorado)
Trestle over Maroon Creek on CO 82 at Aspen
MARQUETTE (shipwreck) (Ashland County, Wisconsin)
Marr's Creek Bridge (Randolph County, Arkansas)
Marshall's Bridge (Chester County, Pennsylvania)
Marshlands Plantation House (Charleston County, South Carolina)
Marston Water Tower (Story County, Iowa)
Martin, Darwin D., House (Erie County, New York)
Mary's River Covered Bridge (Randolph County, Illinois)
Covered bridge over Little Mary's River northeast of Chester, just off IL 150
Maryland Statehouse (Anne Arundel County, Maryland)
Massachusetts Mental Health Center (Suffolk County, Massachusetts)
Demolished and replaced by new construction
Massachusetts School of Art (Suffolk County, Massachusetts)
Massachusetts Statehouse (Suffolk County, Massachusetts)
Massacoe Forest Pavilion (Hartford County, Connecticut)
Matawan Station (Monmouth County, New Jersey)
Mathew Geary House (Mackinac County, Michigan)
Matthews Hall (Maricopa County, Arizona)
Maurice Meyer Barracks (Rogers County, Oklahoma)
Maurice River Lighthouse (Cumberland County, New Jersey)
Maxwell Place (Fayette County, Kentucky)
Mayo Hall (Hunt County, Texas)
Maysville-Aberdeen Bridge (Mason County, Kentucky)
McAlester Armory (Pittsburg County, Oklahoma)
McClay's Twin Bridge (East) (Franklin County, Pennsylvania)
Stone arch bridge over a branch of Conodoguinet Creek on McClays Mill Road (PA 4018)
McClay's Twin Bridge (West) (Franklin County, Pennsylvania)
Stone arch bridge over Conodoguinet Creek on PA 4018
McCoy House (Mifflin County, Pennsylvania)
McElwain House (Aroostook County, Maine)
McKeen Motor Car #70 (Carson City, Nevada)
A self propelled rail passenger car
McKees Rocks Bridge (Allegheny County, Pennsylvania)
Steel through arch bridge over Ohio River on Chartiers Avenue in Pittsburgh
McKinley High School (Honolulu County, Hawaii)
McKinney Homestead (Travis County, Texas)
McLellan House (Cumberland County, Maine)
McMaster School (Richland County, South Carolina)
McMillin Bridge (Pierce County, Washington)
McNabb Mines (Marion County, Tennessee)
McNeese State University Auditorium (Calcasieu Parish, Louisiana)
Meadow Bridge (Coos County, New Hampshire)
Pratt through truss bridge over Androscoggin River in Shelburne
Meadow Brook Farms (Oakland County, Michigan)
Medburyville Bridge (Windham County, Vermont)
Medfield State Hospital (Norfolk County, Massachusetts)
Media Armory (Delaware County, Pennsylvania)
Meems Bottom Covered Bridge (Shenandoah County, Virginia)
Covered bridge on Wissler Road near Mount Jackson
Melrose (Delaware County, Pennsylvania)
Memorial Building (Shawnee County, Kansas)
Memorial Gymnasium (Charlottesville, Virginia)
Memorial Gymnasium (Latah County, Idaho)
Memorial Hall (New Castle County, Delaware)
Memphis and Arkansas Bridge (Crittenden County, Arkansas)
Cantilevered through truss bridge over the Mississippi River on I-55 at Memphis
Men's Hall (Monongalia County, West Virginia)
Mentor Graham House (Hughes County, South Dakota)
Meramec State Park Pump House (Franklin County, Missouri)
Meramec State Park Shelter House (Franklin County, Missouri)
Merrill Hall (Franklin County, Maine)
Merrimac Ferry (Unspecified county, Wisconsin)
Ferry across Wisconsin River on Wis 113
Metal Shop (Champaign County, Illinois)
Metamora Courthouse (Woodford County, Illinois)
Metropolitan State Hospital (Middlesex County, Massachusetts)
Mostly demolished and redeveloped
Miami And Erie Canal, Deep Cut (Allen County, Ohio)
Miami Circle at Brickell Point Site (Miami-Dade County, Florida)
Miamisburg Mound (Montgomery County, Ohio)
Mianus River Railroad Bridge (Fairfield County, Connecticut)
Michael Brisbois House (Crawford County, Wisconsin)
Michigan State Capitol (Ingham County, Michigan)
Michigan State Prison (Jackson County, Michigan)
Mickles Bridge (Yell County, Arkansas)
Middlebury Gorge Concrete Arch Bridge (Addison County, Vermont)
Middlesex Fells Reservation Parkways (Middlesex County, Massachusetts)
Middlesex--Winooski River Bridge (Washington County, Vermont)
Milford Point Hotel (New Haven County, Connecticut)
Military Drill Hall and Men's Gymnasium (Champaign County, Illinois)
Military Park (Marion County, Indiana)
Military Road School (Washington, District of Columbia)
Millen House (Monroe County, Indiana)
Miller Hall (Dawes County, Nebraska)
Miller--Brewer House (Thurston County, Washington)
Millington Station (Morris County, New Jersey)
Million Dollar Bridge (Valdez-Cordova Census Area, Alaska)
Four-span through truss bridge over Copper River on Copper River Highway
Millville Town Site (Jo Daviess County, Illinois)
Milton Armory (Northumberland County, Pennsylvania)
Milwaukee-Downer "Quad" (Milwaukee County, Wisconsin)
Four A.C. Eschweiler designed buidlings that were the basis of Milwaukee Downer College.
Minco Armory (Grady County, Oklahoma)
Mindoro Cut (La Crosse County, Wisconsin)
A hand-hewn cut through hard rock, built in 1907-08, remaining virtually unchanged
Mineral Bluff Depot (Fannin County, Georgia)
Miners Union Hall (Granite County, Montana)
Minneapolis Armory (Hennepin County, Minnesota)
Minnesota Historical Society Building (Ramsey County, Minnesota)
Minnesota Soldiers' Home Historic District (Hennepin County, Minnesota)
Minnesota State Capitol (Ramsey County, Minnesota)
Minnesota State Training School (Goodhue County, Minnesota)
Mission Church (Mackinac County, Michigan)
Missisquoi River Bridge (Franklin County, Vermont)
Mississippi Federation of Women's Clubs (Hinds County, Mississippi)
Mississippi Governor's Mansion (Hinds County, Mississippi)
Mississippi State Capitol (Hinds County, Mississippi)
Missouri Governor's Mansion (Cole County, Missouri)
Missouri State Fairgrounds Historic District (Pettis County, Missouri)
Buildings of the State Fairgrounds of Missouri
Mitchell Hall (Latimer County, Oklahoma)
MKT Boonville Depot (Cooper County, Missouri)
Model School (Stearns County, Minnesota)
Mohawk Trail (Berkshire County, Massachusetts)
Monroe Furnace (Huntingdon County, Pennsylvania)
Monroe Hill (Charlottesville, Virginia)
Monson Developmental Center (Hampshire County, Massachusetts)
Montana Deaf and Dumb Asylum (Jefferson County, Montana)
Montana State Arsenal, Armory and Drill Hall (Lewis and Clark County, Montana)
Montana State Capitol Building (Lewis and Clark County, Montana)
Montana State Normal School (Beaverhead County, Montana)
Montana Territorial and State Prison (Powell County, Montana)
Montana Veterans and Pioneers Memoiral Building (Lewis and Clark County, Montana)
Montauk State Park Open Shelter (Dent County, Missouri)
Montebello (Charlottesville, Virginia)
Montgomery Bell Tunnel (Cheatham County, Tennessee)
Montgomery Hall (Oktibbeha County, Mississippi)
Montopolis Bridge (Travis County, Texas)
Montpelier (Prince George's County, Maryland)
Montrose Mansion and Chapel (Baltimore County, Maryland)
Montrose Schoolhouse (Montgomery County, Maryland)
Monument to Confederate Women (Pulaski County, Arkansas)
Mookini Heiau (Hawaii County, Hawaii)
Mordecai Lincoln House (Washington County, Kentucky)
Morea (Charlottesville, Virginia)
Morehead State University (Rowan County, Kentucky)
Mormon Flat Bridge (Maricopa County, Arizona)
Morrill Hall (Story County, Iowa)
Morris Park Station (Bronx County, New York)
Morris Plains Station (Morris County, New Jersey)
Morris Wide Water Canal Boat Site (Grundy County, Illinois)
Morrow Plots, University of Illinois (Champaign County, Illinois)
Morton Homestead (Delaware County, Pennsylvania)