Illinois - Criteria: C (architecture/engineering)
| Meekerville Historic District |
| Meetinghouse of the Central Congregational Church |
| Melwood Apartments |
| Memorial Washington Reformed Presbyterian Church |
| Menard, Pierre, House |
| Mercer County Jail |
| Mermaid House Hotel |
| Mershon, Joab, House |
| Metal Shop |
| Metamora Courthouse |
| Methodist Episcopal Church |
| Meyer, Pearl and Bess, House |
| Michigan-Lee Apartments |
| Michigan-Wacker Historic District |
| Middletown Historic District |
| Midwest Athletic Club |
| Military Drill Hall and Men's Gymnasium |
| Milk, Lemuel, Carriage House |
| Millard, George Madison, House |
| Millard, Sylvester, House |
| Millburn Historic District |
| Miller, Allan, House |
| Miller, Bell, Apartments |
| Miller, George H., House |
| Miller, Henry W., House |
| Miller, Joseph, House |
| Millikin, James, House |
| Millward, Caroline, House |
| Milne, Robert, House |
| Mineola Hotel |
| Moats, William, Farm |
| Mobile and Ohio Railroad Depot |
| Moline Downtown Commercial Historic District |
| Monadnock Block |
| Monmouth Courthouse Commercial Historic District |
| Montgomery, John Rogerson, House |
| Montgomery Ward Company Complex |
| Monticello Courthouse Square Historic District |
| Moore, C. H., House |
| Morgan County Courthouse |
| Morgan-Wells House |
| Morris Downtown Commercial Historic District |
| Morrison Main Street Historic District |
| Morris Wide Water Canal Boat Site |
| Morse, Robert Hosmer, House |
| Morton, Asher, Farmstead |
| Morton, J. Sterling, High School East Auditorium |
| Moss, Henry Clay, House |
| Motley, John Lothrop, School |
| Motor Row Historic District |
| Mound City National Cemetery |
| Mount Carroll Historic District |
| Mount Lookout |
| Mount Pulaski Courthouse |
| Mount Sterling Commercial Historic District |
| Muirhead, Robert and Elizabeth, House |
| Mundelein College Skyscraper Building |
| Municipal Courts Building |
| Murphysboro Elks Lodge |
| Nachusa House |
| Naperville Historic District |
| Naples Archeological District |
| Narodni Sin |
| Narragansett, The |
| Natural History Building |
| Near North Historic District |
| Neuville, The |
| Newcomb, Richard F., House |
| New Masonic Building and Oriental Theater |
| New Orpheum Theatre |
| Nichols, Harry H., House |
| Nickerson, Samuel, House |
| Nisbet Homestead Farm |
| Normal Theater |
| Northeast Evanston Historic District |
| North Eighth Street Plaza |
| North Geneva Historic District |
| North Sangamon United Presbyterian Church |
| North Shore Sanitary District Tower |
| North Side Historic District |
| North State Street Historic District |
| North Wells Street Historic District |
| Norwood Park Historical District |
| Notre Dame de Chicago |
| Oak Circle Historic District |
| Oaklawn Farm |
| Oak Park Conservatory |
| Oak Ridge Apartments |
| Oak Ridge Cemetery |
| Oakton Gables |
| Oakton Historic District |
| O'Connell, Daniel, House |
| O'Conor, Andrew J., III, House |
| Octagon House |
| Ogle County Courthouse |
| O'Grady, Mr. J. William de Coursey, House |
| Old Cahokia Courthouse |
| Old Chicago Historical Society Building |
| Old Colony Buildings |
| Old Customhouse |
Data from United States Park Service and Wikidata
