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County Map of Missouri

Figure 1: County map of Missouri. Click on the map to see a larger version with surrounding states. A map with clickable counties is also available. Based on data from MSDIS (2009).

Missouri borders eight other states, more than any other state (except Tennessee, which also borders eight). Four of the states share an artificial geopolitical boundary with Missouri: Iowa, to the north; Kansas, to the west; Arkansas, to the south; and Oklahoma, to the southwest. The other four are separated from Missouri by a major river: Nebraska, separated by the Missouri River to the northwest; and Illinois, Kentucky, and Tennessee, separated by the Misssissippi River, to the east and southeast, respectively.

The state has significant faunal and floral elements from each of the cardinal directions. Northern species, such as the Four-toed Salamander (Hemidactylium scutatum) and Wood Frog (Lithobates sylvaticus) established populations in the Ozarks and northeast Missouri during a glacial advance and have persisted into modern times.

The Ozarks are a part of the Interior Highlands, a western extension of the Eastern Temperate Forest region. Brook Salamanders (Eurycea) and Woodland Salamanders (Plethodon) both have representatives in the state that are endemic to the region as well as some species that are more widespread. Also, the majority of Missouri's reptiles and amphibians are considered eastern species.

Western species are also found in the Ozarks and along prairie regions in the western part of the state. The Collared Lizard (Crotaphytus collaris) and Flat-headed Snake (Tantilla gracilis) are found on Ozark glades, while species such as the Great Plains Skink (Plestiodon obsoletus) and Variable Groundsnake (Sonora semiannulata) are found in scattered localities in Missouri but are much more common to the west.

The Mississippi Alluvial Plain in southeast Missouri is home to many species that find the northern limit of their range here. This includes the Mole Salamander (Ambystoma talpoideum), Three-toed Amphiuma (Amphiuma tridactylum), Southern Watersnake (Nerodia fasciata), Mississippi Mud Turtle (Kinosternon subrubrum), and several others. Many of these southeastern species are confined (or nearly so) to this region and are found with other species that are more widespread in the state. Read more about terrestrial ecoregions in Missouri.

Missouri is also home to the confluence of the three largest rivers in the nation. The Mississippi and Missouri River, both of which form an important natural portion of the state, join together in Columbia Bottoms north of Saint Louis. The Mississippi River then joins the Ohio River, flowing from the east, just across from Mississippi County. The northern 2/3 of the state is drained by the Mississippi or Missouri, but the southern 1/3 is drained by tributaries of the Arkansas River or White River.

Naturally, some species are highly dependent on rivers as a habitat. This includes map turtles (Graptemys) and softshell turtles (Apalone) as well as our large salamanders, the Hellbender (Cryptobranchus alleganiensis) and Mudpuppy (Necturus maculosus), among others. However, there are also some species that appear to be reliant upon the habitat created by the rivers. The Western Foxsnake (Pantherophis vulpinus) appears to be restricted to habitat near the large rivers in the northern part of the state, even though it is not particularly associated with rivers elsewhere in its range. There are also several Great Plains anurans, most notably the Great Plains Toad (Anaxyrus cognatus) and Plains Spadefoot (Spea bombifrons), that appear to rely on cultivated river bottoms along the Missouri River as a proxy to their loose soil habitats in the plains. Read more about rivers and watersheds.

The state is comprised of 114 counties (Figure 1) and the independent city of Saint Louis (which has been combined in the MOHAP project with Saint Louis County for practical reasons). This site contains a page for each county that lists its herpetofauna, a collection summary, and a list of potential new records for the county. Click on a county name in Table 1 (below) or use the clickable county map and click a county map to see the detailed page for that county. A labelled map is also available.

Table 1. County list for Missouri. County names are links to detailed information about that county. A labelled county map and a map with clickable counties is also available.

Adair Clay Iron Montgomery Saint Clair
Andrew Clinton Jackson Morgan Sainte Genevieve
Atchison Cole Jasper New Madrid Saint Francois
Audrain Cooper Jefferson Newton Saint Louis
Barry Crawford Johnson Nodaway Saint Louis City
Barton Dade Knox Oregon Saline
Bates Dallas Laclede Osage Schuyler
Benton Daviess Lafayette Ozark Scotland
Bollinger De Kalb Lawrence Pemiscot Scott
Boone Dent Lewis Perry Shannon
Buchanan Douglas Lincoln Pettis Shelby
Butler Dunklin Linn Phelps Stoddard
Caldwell Franklin Livingston Pike Stone
Callaway Gasconade Macon Platte Sullivan
Camden Gentry Madison Polk Taney
Cape Girardeau Greene Maries Pulaski Texas
Carroll Grundy Marion Putnam Vernon
Carter Harrison McDonald Ralls Warren
Cass Henry Mercer Randolph Washington
Cedar Hickory Miller Ray Wayne
Chariton Holt Mississippi Reynolds Webster
Christian Howard Moniteau Ripley Worth
Clark Howell Monroe Saint Charles Wright


Missouri Level I Ecoregions

Figure 2: Level I Ecoregions in Missouri and surrounding states. Click to see a labelled map. Modified from EPA (2003). Base map from National Atlas (2001).

Missouri Level II Ecoregions

Figure 3: Level II Ecoregions in Missouri and surrounding states. Click to see a labelled map. Modified from EPA (2003). Base map from National Atlas (2001).

Missouri Level III Ecoregions

Figure 4: Level III Ecoregions in Missouri and surrounding states. Click to see a labelled map. Modified from EPA (2003). Base map from National Atlas (2001).

Missouri Level IV Ecoregions

Figure 5: Level IV Ecoregions in Missouri and surrounding states. Click to see a labelled map. Modified from EPA (2003). Base map from National Atlas (2001).

An ecoregion classification system attempts to define and describe geographic regions that correspond to broad ecosystem patterns, topography, geology, soils, vegetation patterns, and the distributions of plants and animals. Omernik (1987) described ecoregions (Levels I, II, and III) for the conterminous United States as a hierarchical scheme with Level I corresponding to large regions and Level II and Level III representing successively smaller and more precisely described regions. The Environmental Protection Agency (2003) is coordinating an effort to further subdivide Level III regions into Level IV regions. Nigh and Schroeder (2002) published Level III and Level IV ecoregions for Missouri.

Some amphibian and reptile species follow defined ecoregions closely. For example, the Cave Salamander (Eurycea lucifuga) is neatly confined to the Ozark Highlands (Level III) and found throughout the ecoregion, with the exception of most of the Springfield Plateau (Level IV). Several species found in the southeastern alluvial plain are particularly characteristic and also confined to that area (e.g., Three-toed Amphiuma (Amphiuma tridactylum) and Southern Watersnake (Nerodia fasciata)).

Many species, however, seem to be abundant throughout Missouri, regardless of the region or natural community. The Bullfrog (Lithobates catesbeianus), Eastern Snapping Turtle (Chelydra serpentina), and Western Ratsnake (Pantherophis obsoletus) among several others fall into this category.

Finally, many species are more closely associated with a particular natural community or habitat than with a particular ecoregion or natural division. For example, The Flat-headed Snake (Tantilla gracilis) can be found in the Ozark Highlands, Osage Prairie, and Interior River Valleys and Hills but it is restricted to rocky glades.

In general, Level IV ecoregions are too granular to be useful in describing the distributions of Missouri amphibians and reptiles, several Ozark salamander species and many of the coastal plains species being notable exceptions. However, this level of detail is useful to understand natural community distributions on which some species are dependent. It also underscores the importance of looking at border states and across artificial political boundaries to understand distributions within Missouri.

Level I (Figure 2), Level II (Figure 3), Level III (Figure 4), and Level IV (Figure 5) ecoregion maps for Missouri and surrounding states, based on Omernik (1987) and Nigh and Schroeder (2002) are included here. The hierarchy for all levels are included in Table 2 (below). Unfortunately, the authors' coding scheme for Level III is inconsistent, though the names do match. Both authors' codes for Level III are included as a cross-reference. For example, Omernik coded the Ozark Highlands as 8.4.5, but Nigh and Schroeder used 39 for the same region.

Table 2. Ecoregion hierarchy for Missouri, based on Omernik (1987) and Nigh and Schroeder (2002). Those regions marked with an asterisk (*) do not occur in Missouri but are sufficiently close to be of interest to Missouri biologists. Those regions marked with a caret (^) are contained entirely within the state’s borders.

Prior to Omernik's ecoregion classification scheme, Thom and Wilson (1980) divided Missouri into natural divisions and sections (Figure 6), roughly corresponding to Level III and Level IV ecoregions, respectively. Although the boundaries are a bit different in some cases, most regions are easily recognized between the two schemes. Thom and Wilson's work is included here, particularly since they used historical names (e.g., Crowley's Ridge) for some regions rather than the more generic terms used by the ecoregion authors. A complete list of Missour's natural division and sections can be found in Table 3.

Missouri natural divisions and sections

Figure 6: Natural divisions and sections of Missouri. Key to natural divisions and sections is contained within the main text. Click on the map to see a larger version. Modified from Thom and Wilson (1980). Base map from MSDIS (2009) and MDC (2007).

Table 3. List of Missouri Natural Divisions and Sections.

Rivers and Watersheds

Missouri rivers and major streams

Figure 7: Major rivers and streams in Missouri. Click to see a labelled map. Modified from MDC (2007) and USGS (1994).

Major Missouri watersheds

Figure 8: Major Missouri watersheds. Click to see a labelled map. Based on data from NRCS (2002). Base map from MSDIS (2009).

Missouri is home to four major river drainages: a) Mississippi River, b) Missouri River, c) Arkansas River, and d) White River, with the latter three ultimately flowing into the Mississippi. Included within these drainages are dozens of larger rivers (Table 4, Figure 7) and hundreds of small streams. Aquatic habitats play an important role in the lives and distributions of several species of amphibians and reptiles. Some species found in the state exhibit distributions that can be better understood by referring to these primary drainage systems rather than terrestrial classification schemes, such as those described above.

Watersheds are defined as the land area drained by a specific river or stream system. Since rivers and streams vary greatly in size and the corresponding land they drain, a watershed classification system normally settles on watersheds that are roughly the same size. One such classification system can be seen in Figure 8. Note that watersheds are naturally hierarchical in nature. For example, the Niangua River watershed is one part of the larger Missouri River watershed, which is itself part of the Mississippi River watershed.

For most terrestrial organisms, drainages or watersheds are often of little consequence and can be ignored. But, for those animals that are restricted to rivers, like the Hellbender (Cryptobranchus alleganiensis), Mudpuppy (Necturus maculosus), or softshell turtles (Apalone), the drainage patterns of the rivers are far more important than terrestrial ecoregions. On plateaus, such as the Ozarks, streams from two different watersheds that are otherwise hardly separated from one another are literally hundreds of miles apart from the perspective of obligate aquatic organisms.

Table 4. Major Missouri rivers and tributaries in Missouri listed in stream order. To avoid confusion, the four drainages are separated though in reality, the Arkansas, Missouri, and White Rivers are all tributaries of the Mississippi. These four primary drainages are in bold.

Like terrestrial ecoregions, aquatic subregions can be classified in discrete units, based on watershed and hydrological characteristics. Subregions are composed of ecological drainage units, which are major watersheds that are consolidated based on similarity and proximity (MSDIS 2009).

The ecological drainage units map (Figure 9) shows a somewhat consolidated view of the watersheds map based on those watersheds and other characteristics. It is underlain with unique background colors showing the three broad aquatic subregions in the state. Still more detailed aquatic region classifications are available but often include areas based on very small creeks and their watersheds and are therefore beyond the scope of a study of Missouri's herpetofaunal distributions. Aquatic subregions and their component drainage units can be seen in Table 5 (below).

Naturally, many of the same patterns emerge in both terrestrial and aquatic geographic classifications since the two are not independent of one another. However, aquatic subregions and ecological drainage units can differ from their terrestrial counterparts since most aquatic organisms are confined to watersheds as well as specific habitats. Since many species of amphibians and reptiles are partially or wholly dependent on aquatic habitats, distributions can sometimes be best understood and explained by examining aquatic subregions, ecological drainage units, and even individual watersheds.

Missouri Ecological Drainage Units

Figure 9: Missouri Ecological Drainage Units. Click to see a labelled map. Based on data from MSDIS (2009).

Table 5. List of Aquatic Subregions and Ecological Drainage Units from MSDIS (2009). Each drainage unit is indicated with its primary drainage system: a) Mississippi River, b) Missouri River, c) Arkansas River, d) White River.

Literature Cited