The America's Byways® collection is distributed through most of the 50 States and thus is broadly representative of driving experiences across the nation. In order to be truly representative of the United States though, this collection should encompass the great diversity of landforms, natural landscapes, and cultural opportunities that exist in the country. For that reason, it is useful to look at thematic maps of the United States with the America's Byways® collection overlaid.
Map 2 shows the America's Byways® collection in relation to the 50 "Level II" ecological regions ("ecoregions") of North America as recognized by the U.S. Environmental Protection Agency. The Level II ecoregions show ecological patterns at the national and subcontinental scales. The map indicates the ecological diversity represented by currently designated byways, including those designated for people-based intrinsic qualities (archeological, cultural, and historic) as well as the land-based qualities (natural, recreational, and scenic) that are more closely associated with ecoregions.
Map 2 : America's Byways® and North American Level II Ecological Regions
While designated byways are well represented in mountainous areas such as the Cascades, the Sierra Nevada, the Rockies, and the Appalachians, they are relatively sparse in large areas of the western desert States, the Great Basin, and even to some degree in the southeastern coastal plains. This unequal representation of American landforms and environments may have much to do with an emphasis on scenic quality in the Program, and a broad appreciation for dramatic scenery of mountains and coastlines.
Map 2 does not show Hawaii or Puerto Rico because these are not included in the North American ecoregion typology. However, Hawaii has five tropical and subtropical ecoregions and Puerto Rico three, none of which occur in North America. Thus, the absence of designated byways in these two areas means that several nationally distinctive ecoregions are unrepresented in the America's Byways collection.
Ecological regions are excellent baselines for assessing the landscape diversity of the existing collection of byways. Similar maps exist for other environmental descriptors, including the following: