Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Lake Marcel Dam | Dam | 90 | King | 47 41 35 N | 121 55 04 W |
| Lake Margaret Dam | Dam | 252 | King | 47 45 59 N | 121 54 04 W |
| Lake Marney Dam | Dam | 797 | Pend Oreille | 48 12 24 N | 117 14 58 W |
| Lake Martindale Dam | Dam | 51 | King | 47 22 41 N | 122 18 40 W |
| Lake Padden Dam | Dam | 137 | Whatcom | 48 42 17 N | 122 27 47 W |
| Lake Shoecraft Outlet Dam | Dam | 100 | Snohomish | 48 07 35 N | 122 18 23 W |
| Lake Tapps Dike Number 10 | Dam | 167 | Pierce | 47 14 23 N | 122 09 22 W |
| Lake Tapps Dike Number 11 | Dam | 167 | Pierce | 47 14 05 N | 122 08 52 W |
| Lake Tapps Dike Number 12 | Dam | 165 | Pierce | 47 13 47 N | 122 08 40 W |
| Lake Tapps Dike Number 13 | Dam | 169 | Pierce | 47 11 23 N | 122 09 52 W |
| Lake Tapps Dike Number 2A | Dam | 168 | Pierce | 47 14 59 N | 122 11 16 W |
| Lake Tapps Dike Number 2B | Dam | 166 | Pierce | 47 14 59 N | 122 11 10 W |
| Lake Tapps Dike Number Eight Dam | Dam | 166 | Pierce | 47 14 23 N | 122 09 40 W |
| Lake Tapps Dike Number Five Dam | Dam | 167 | Pierce | 47 14 23 N | 122 10 04 W |
| Lake Tapps Dike Number Four Dam | Dam | 160 | Pierce | 47 14 29 N | 122 10 16 W |
| Lake Tapps Dike Number Nine Dam | Dam | 166 | Pierce | 47 14 23 N | 122 09 34 W |
| Lake Tapps Dike Number One Dam | Dam | 175 | Pierce | 47 14 29 N | 122 11 04 W |
| Lake Tapps Dike Number Seven Dam | Dam | 166 | Pierce | 47 14 23 N | 122 09 46 W |
| Lake Tapps Dike Number Six Dam | Dam | 167 | Pierce | 47 14 17 N | 122 09 52 W |
| Lake Tapps Dike Number Three Dam | Dam | 131 | Pierce | 47 15 53 N | 122 10 40 W |
| Lake West Dam | Dam | 165 | Franklin | 46 36 04 N | 118 15 12 W |
| Lake Youngs Inlet Dam | Dam | 146 | King | 47 25 05 N | 122 06 28 W |
| Lakes Unlimited Dam | Dam | 288 | Snohomish | 47 46 53 N | 121 55 52 W |
| Lamb-Weston Dam | Dam | 250 | Franklin | 46 39 12 N | 118 52 52 W |
| Lang Dam Number One | Dam | 79 | Skagit | 48 23 41 N | 122 16 59 W |
| Lang Dam Number Three | Dam | 85 | Skagit | 48 23 53 N | 122 16 53 W |
| Lang Dam Number Two | Dam | 83 | Skagit | 48 23 47 N | 122 16 59 W |
| Lawson Dam Number One | Dam | 6 | San Juan | 48 29 35 N | 123 01 25 W |
| Lawson Dam Number Two | Dam | 129 | San Juan | 48 32 41 N | 123 07 53 W |
| Lawson Lake Dam | Dam | 92 | San Juan | 48 32 47 N | 123 07 23 W |
| Leader Lake Dam | Dam | 691 | Okanogan | 48 21 42 N | 119 41 52 W |
| Leader Lake Saddle Dam | Dam | 688 | Okanogan | 48 21 30 N | 119 41 04 W |
| Lehman Pond Dam | Dam | 40 | San Juan | 48 38 17 N | 123 00 23 W |
| Lemansky Lake Dam | Dam | 1106 | Okanogan | 48 42 06 N | 119 37 34 W |
| Lenhard Reservoir Dam | Dam | 655 | Stevens | 47 56 60 N | 117 33 28 W |
| Lenice Dam | Dam | 169 | Grant | 46 50 41 N | 119 50 34 W |
| Leroy Anderson Dam | Dam | 276 | Clark | 45 52 41 N | 122 27 58 W |
| Lester Creek Reservoir Dam | Dam | 282 | Lewis | 46 32 05 N | 123 18 47 W |
| Lewis Dam | Dam | 141 | Kitsap | 47 33 59 N | 122 51 53 W |
| Libby Lake Dam | Dam | 2310 | Okanogan | 48 14 30 N | 120 20 16 W |
| Lily Lake Dam | Dam | 939 | Chelan | 47 17 47 N | 120 18 28 W |
| Lincoln Heights Reservoir Dam | Dam | 687 | Spokane | 47 37 60 N | 117 21 52 W |
| Lincoln Park Reservoir Dam | Dam | 99 | King | 47 36 59 N | 122 19 10 W |
| Lindstrom Dam Number One | Dam | 216 | Pierce | 46 58 35 N | 122 14 28 W |
| Lindstrom Dam Number Two | Dam | 216 | Pierce | 46 58 35 N | 122 14 28 W |
| Little Brush Lake Dam | Dam | 193 | Skamania | 45 41 56 N | 121 55 40 W |
| Little Falls Dam | Dam | 399 | Lincoln | 47 49 48 N | 117 55 04 W |
| Little Falls Dam | Dam | 401 | Stevens | 47 49 48 N | 117 55 04 W |
| Little Goose Lock and Dam | Dam | 196 | Whitman | 46 35 15 N | 118 01 34 W |
| Little Green Lake Dam | Dam | 476 | Okanogan | 48 26 12 N | 119 37 52 W |
| Little Quilcene River Dam | Dam | 254 | Jefferson | 47 52 04 N | 122 56 17 W |
| Little Spokane River Dam | Dam | 684 | Pend Oreille | 48 08 06 N | 117 21 10 W |
| Little Twin Lakes Dam | Dam | 1135 | Stevens | 48 34 12 N | 117 38 40 W |
| Little White Salmon Hatchery Dam | Dam | 73 | Skamania | 45 43 17 N | 121 38 34 W |
| Littletwin Lakes Dam | Dam | 48 | Mason | 47 12 59 N | 122 58 23 W |
| Locke Dam | Dam | 728 | Pend Oreille | 48 25 36 N | 117 19 34 W |
| Loers Dam | Dam | 32 | Island | 48 17 11 N | 122 41 23 W |
| Long Dam | Dam | 896 | Klickitat | 45 56 35 N | 120 22 22 W |
| Long Lake Dam | Dam | 495 | Stevens | 47 50 14 N | 117 50 22 W |
| Long-Bell Mill Pond Dam | Dam | 213 | Lewis | 46 28 29 N | 122 28 52 W |
| Loon Lake Dam | Dam | 731 | Stevens | 48 03 30 N | 117 39 04 W |
| Lords Lake East Dam | Dam | 291 | Jefferson | 47 52 53 N | 122 55 53 W |
| Lords Lake North Dam | Dam | 337 | Jefferson | 47 53 17 N | 122 56 11 W |
| Loreene Lake Dam | Dam | 66 | King | 47 18 41 N | 122 23 10 W |
| Louise Lake Dam | Dam | 110 | Whatcom | 48 42 41 N | 122 19 35 W |
| Loup Loup Dam | Dam | 733 | Okanogan | 48 22 60 N | 119 45 52 W |
| Loutsis Dam | Dam | 49 | King | 47 43 17 N | 121 58 46 W |
| Lovitt Tailing Pond Dam | Dam | 307 | Chelan | 47 22 47 N | 120 18 52 W |
| Lower Cushman Dam | Dam | 145 | Mason | 47 23 51 N | 123 12 04 W |
| Lower Dam | Dam | 477 | King | 47 24 45 N | 121 45 09 W |
| Lower Goose Lake Dam | Dam | 264 | Grant | 46 55 06 N | 119 17 04 W |
| Lower Granite Lake Dam | Dam | 226 | Whitman | 46 39 38 N | 117 25 41 W |
| Lower Monumental Dam | Dam | 166 | Franklin | 46 33 45 N | 118 32 15 W |
| Lower Pine Lake Dam | Dam | 679 | Spokane | 47 23 54 N | 117 32 40 W |
| Lower Rimrock Dam | Dam | 428 | Douglas | 47 29 35 N | 119 45 28 W |
| Luhr Creek Dam | Dam | 12 | Pierce | 47 12 59 N | 122 42 46 W |
| Lummi Island Est. Dam | Dam | 154 | Whatcom | 48 40 47 N | 122 38 29 W |
| Lynda Lake Dam | Dam | 859 | Pend Oreille | 48 02 54 N | 117 08 34 W |
| Lyon Lake Dam | Dam | 344 | Grant | 47 16 24 N | 119 19 46 W |
| Lyons Dam | Dam | 165 | Franklin | 46 35 32 N | 118 13 34 W |
| Magnolia Manor Reservoir Dam | Dam | 84 | King | 47 39 05 N | 122 23 28 W |
| Malinowski Dam | Dam | 142 | Grays Harbor | 47 15 41 N | 123 42 53 W |
| Maple Leaf Reservoir Dam | Dam | 130 | King | 47 41 23 N | 122 18 58 W |
| Margos Lake Dam | Dam | 21 | San Juan | 48 31 35 N | 123 06 11 W |
| Mark Res Dam | Dam | 645 | Klickitat | 45 45 17 N | 121 09 28 W |
| Marona Mill Pond Dam | Dam | 103 | Whatcom | 48 43 05 N | 122 12 53 W |
| Marsh Unit One Dam | Dam | 276 | Grant | 46 57 30 N | 119 15 40 W |
| Marshall Lake Dam | Dam | 832 | Pend Oreille | 48 15 24 N | 117 04 34 W |
| Martin Creek Dam | Dam | 161 | Pacific | 46 41 53 N | 123 46 53 W |
| Martins Lake Dam | Dam | 147 | San Juan | 48 37 23 N | 122 53 29 W |
| Marvin Eberle Dam | Dam | 275 | Yakima | 46 17 59 N | 119 53 58 W |
| Masonry Dam | Dam | 477 | King | 47 24 44 N | 121 45 11 W |
| Mathison Reservoir Dam | Dam | 710 | Chelan | 47 18 53 N | 120 16 52 W |
| Matsuda Reservoir Dam | Dam | 125 | King | 47 25 53 N | 122 27 58 W |
| Mayfield Dam | Dam | 131 | Lewis | 46 30 10 N | 122 35 17 W |
| McAllister Spring Lake Dam | Dam | 3 | Thurston | 47 01 41 N | 122 43 28 W |
| McCoy Creek Dam | Dam | 101 | Snohomish | 47 50 35 N | 121 49 22 W |
| McDonald Dam | Dam | 546 | Grant | 47 38 54 N | 119 06 34 W |
| McDowell Lake Dam | Dam | 703 | Stevens | 48 28 12 N | 117 40 58 W |
| McGlinchy Dam | Dam | 72 | Snohomish | 47 55 47 N | 122 08 04 W |
| McGregory Dam | Dam | 395 | Whitman | 46 39 60 N | 118 09 34 W |
| McKay Dam | Dam | 883 | Douglas | 47 41 47 N | 120 03 46 W |
| McLaughlin Dam | Dam | 685 | Chelan | 47 19 53 N | 120 14 58 W |
| McMillin North Reservoir Number One Dam | Dam | 179 | Pierce | 47 08 05 N | 122 15 22 W |
| McMillin Reservoir Number Two Dam | Dam | 179 | Pierce | 47 07 47 N | 122 15 22 W |
| McMillin South Reservoir Number One Dam | Dam | 179 | Pierce | 47 07 59 N | 122 15 22 W |
| McNary Dam | Dam | 105 | Benton | 45 56 10 N | 119 17 50 W |
| Meadow Lake Dam | Dam | 267 | Chelan | 47 21 41 N | 120 12 52 W |
| Meadow Springs Dam | Dam | 141 | Benton | 46 13 35 N | 119 15 40 W |
| Medicine Creek Reservoir Dam | Dam | 5 | Thurston | 47 03 17 N | 122 43 34 W |