| City on the Merrimack | 21 |
| City on the Merrimack River | 27 |
| City on the Meurthe | 19 |
| City on the Meuse | 17 |
| City on the Mexican border | 26 |
| City on the Mississippi | 23 |
| City on the Mississippi in ''Huckleberry Finn'' | 63 |
| City on the Mississippi Sound | 29 |
| City on the Missouri River | 26 |
| City on the Mohawk | 18 |
| City on the Mohawk River | 24 |
| City on the Moldau | 18 |
| City on the Mormon Trail | 24 |
| City on the Mosel | 17 |
| City on the Moselle | 19 |
| City on the Moselle River | 25 |
| City on the mouth of the Columbia River | 39 |
| City on the move? | 17 |
| City on the Mures | 17 |
| City on the Natchez Trace | 25 |
| City on the Neckar | 18 |
| City on the Neosho River | 24 |
| City on the Neva | 16 |
| City on the Niagara Escarpment | 30 |
| City on the Nile | 16 |
| City on the Nile Delta | 22 |
| City on the Nile's east bank | 32 |
| City on the NJ side of the George Washington Bridge | 51 |
| City on the north end of the Golden Gate Bridge | 47 |
| City on the North Platte | 24 |
| City on the Oca | 15 |
| City on the Ocmulgee | 20 |
| City on the Ocmulgee River | 26 |
| City on the Oder | 16 |
| City on the Odra | 16 |
| City on the Ohio | 16 |
| City on the Oka | 15 |
| City on the Oka River | 21 |
| City on the Oka, near Moscow | 28 |
| City on the Oregon Trail | 24 |
| City on the Orne | 16 |
| City on the Ouche | 17 |
| City on the Ouse | 16 |
| City on the Outer Cape of Massachusetts | 39 |
| City on the Pacific | 19 |
| City on the Panama Canal | 24 |
| City on the Pará | 19 |
| City on the Passaic | 19 |
| City on the Penobscot | 21 |
| City on the Penobscot River | 27 |
| City on the Permian Basin | 25 |
| City on the Pina | 16 |
| City on the Po | 14 |
| City on the Puget Sound | 23 |
| City on the Puyallup River | 26 |
| City on the Raccoon | 19 |
| City on the RÃmac River | 26 |
| City on the Red River | 21 |
| City on the Reuss | 17 |
| City on the Reuss River | 23 |
| City on the Rhône | 24 |
| City on the Rhône and Saône | 41 |
| City on the Rhein | 17 |
| City on the Rhine | 17 |
| City on the Rhine, old style | 28 |
| City on the Rhine, to locals | 28 |
| City on the Rhone | 17 |
| City on the Rhone and Saone | 27 |
| City on the Rhone delta | 23 |
| City on the Rhone River | 23 |
| City on the Rideau Canal | 24 |
| City on the Rimac | 17 |
| City on the Rio Grande | 22 |
| City on the River Aire | 22 |
| City on the Riviera | 19 |
| City on the Roaring Fork River | 30 |
| City on the Ruhr | 16 |
| City on the Ruhr River | 22 |
| City on the Saale | 17 |
| City on the Saône | 20 |
| City on the Sabine | 18 |
| City on the Salentine Peninsula | 31 |
| City on the Salt | 16 |
| City on the Salt River | 22 |
| City on the Santa Cruz | 22 |
| City on the Saone and Rhone | 27 |
| City on the Sarthe | 18 |
| City on the Scarpe River | 24 |
| City on the Scheldt | 19 |
| City on the Seine | 17 |
| City on the Seine upstream from Paris | 37 |
| City on the Seward Peninsula | 28 |
| City on the Seyhan | 18 |
| City on the Shatt al-Arab river | 31 |
| City on the Shatt al-Arab waterway | 34 |
| City on the shore of Utah Lake | 30 |
| City on the site of ancient Carthage | 36 |
| City on the Skunk | 17 |
| City on the Skunk River | 23 |
| City on the slopes of Mount Carmel | 34 |