Fig. 7. Ecoregions of the United States after Bailey (1976) with the addition of 10 Marine and Estuarine Provinces proposed in our classification.

^aDomains, Divisions, Provinces, and Sections used on Bailey's (1976) map and described in detail in Bailey (1978). Highland ecoregions are designated M mountain, P plateau, and A altiplano.

1000 Polar                                            
   1200 Tundra                        
      1210 Arctic Tundra
      1220 Bering Tundra                
      M1210 Brooks Range
   1300 Subarctic
      1310 Yukon Parkland
      1320 Yukon Forest
      M1310 Alaska Range
2000 Humid Temperate
   2100 Warm Continental
      2110 Laurentian Mixed Forest
         2111 Spruce-Fir Forest
         2112 Northern Hardwoods-Fir Forest
         2113 Northern Hardwoods Forest
         2114 Northern Hardwoods-Spruce Forest
      M2110 Columbia Forest
         M2111 Douglas-fir Forest
         M2112 Cedar-Hemlock-Douglas-fir Forest
   2200 Hot Continental
      2210 Eastern Deciduous Forest
         2211 Mixed Mesophytic Forest
         2212 Beech-Maple Forest
         2213 Maple-Basswood Forest + Oak Savanna
         2214 Appalachian Oak Forest
         2215 Oak-Hickory Forest
   2300 Subtropical
      2310 Outer Coastal Plain Forest
         2311 Beech-Sweetgum-Magnolia-Pine-Oak
         2312 Southern Floodplain Forest
      2320 Southeastern Mixed Forest
   2400 Marine
      2410 Willamette-Puget Forest
      M2410 Pacific Forest (in conterminous U.S.)
         M2411 Sitka Spruce-Cedar-Hemlock Forest
         M2412 Redwood Forest
         M2413 Cedar-Hemlock-Douglas-fir Forest
         M2414 California Mixed Evergreen Forest
         M2415 Silver fir-Douglas-fir Forest
      M2410 Pacific Forest (in Alaska)
   2500 Prairie
      2510 Prairie Parkland 
         2511 Oak-Hickory-Bluestem Parkland 
         2512 Oak + Bluestem Parkland
      2520 Prairie Brushland 
         2521 Mesquite-Buffalo Grass
         2522 Juniper-Oak-Mesquite
         2523 Mesquite-Acacia
      2530 Tall-Grass Prairie 
         2531 Bluestem Prairie 
         2532 Whestgrass-Bluestem-Needlegrass 
         2533 Bluestem-Gamma Prairie
      2600 Mediterranean (Dry-summer Subtropical)
         2610 California Grassland 
         M2610 Sierran Forest 
         M2620 California Chaparral 
   3000 Dry
      3100 Steppe 
         3110 Great Plains-Shortgrass Prairie 
            3111 Gramma-Needlegrass-Wheatgrass
            3112 Wheatgrass-Needlegrass 
            3113 Grama-Buffalo Grass
         M3110 Rocky Mountain Forest
            M3111 Grand-fir-Douglas-fir Forest
            M3112 Douglas-fir Forest
            M3113 Ponderosa Pine-Douglas-fir Forest
         3120 Palouse Grassland
         M3120 Upper Gila Mountains Forest
         3130 Intermountain Sagebrush
            3131 Sagebrush-Wheatgrass
            3132 Lahontan Saltbush-Greasewood
            3133 Great Basin Sagebrush
            3134 Bonneville Saltbush-Greasewood
            3135 Ponderosa Shrub Forest
         P3130 Colorado Plateau
            P3131 Juniper-Pinyon Woodland + Sagebrush
                 Saltbush Mosaic
            P3132 Grama-Galleta Steppe + Juniper-Pinyon
                 Woodland Mosaic
         3140 Mexican Highland Shrub Steppe
         A3140 Wyoming Basin
            A3141 Wheatgrass-Needlegrass-Sagebrush
            A3142 Sagebrush-Wheatgrass
      3200 Desert
         3210 Chihuahuan Desert
            3211 Grama-Tobosa
            3212 Tarbush-Creosote Bush
         3220 American Desert
            3221 Creosote Bush
            3222 Creosote Bush-Bur Sage
   4000 Humid Tropical
      4100 Savanna
         4110 Everglades
      4200 Rainforest
         M4210 Hawaiian Islands