The common racer has been recorded in each of the 48 states of the
mainland of the United States, also in New Brunswick, Nova Scotia,
southern British Columbia, and southward through Mexico where it is
limited to a narrow strip of east coast lowlands but extends as far as
Guatemala. _C. c. constrictor_ occupies the northeastern states and
extends south into the Appalachian and Piedmont. _C. c. priapus_ with
its associated races _paludicola_, _helvigularis_, and _anthicus_ has
an Austroriparian distribution, occupying the Atlantic Coastal plain
and the Gulf Region, and extending north in the Mississippi Valley to
southern Illinois and Indiana. _C. c. paludicola_ is localized with
two disjunct populations--in the Everglades and on Cape Canaveral,
Florida. _C. c. helvigularis_ is even more restricted in range and is
known only from the Appalachicola region of the Florida Panhandle and
the adjacent corners of Alabama and Georgia. _C. c. anthicus_ occupies
much of central and western Louisiana and adjacent Texas. _C. c.
flaviventris_ occurs throughout the Great Plains, east in the "Prairie
Peninsula" through Michigan and northern Ohio and west to the Rocky
Mountains. _C. c. stejnegerianus_ occurs from Matagorda Bay in Texas
southward through eastern Mexico, with a seemingly isolated population
in the Sierra del Carmen region of northern Coahulia. _C. c. mormon_
occurs in the Pacific Coast states and Great Basin.
Actually, the range limits and the continuity of distribution within
the area outlined are still poorly known. The species has not been
recorded from the northern parts of Maine, Vermont, New Hampshire,
Michigan, Wisconsin, or Minnesota, nor from northeastern New York. It
is generally absent from southwestern desert areas. Records are
particularly scarce and scattered in the Rocky Mountain states,
suggesting that the distribution in this area may be discontinuous. In
a large area comprising all of New Mexico and Arizona, the western
half of Colorado, and the southern halves of Utah and Nevada, records
are so scarce as to indicate that the species is there represented by
only a few well isolated relict colonies. The type locality of
_mormon_ is "Valley of the Great Salt Lake," and there are numerous
records from the northern part of Utah east of Great Salt Lake
(Woodbury, 1931:75), but a record from Moab is the only one known to
me from the southern half of the state. The only records from western
Colorado are from three miles east of Fruita and two miles west of
Grand Junction, Mesa County (Maslin, 1959:56). Apparently the only
valid record from Arizona is that of Shannon (1950:59) from Eagar,
Apache County, in the east-central part. Shannon also recorded the
racer from Boulder Dam in extreme southern Nevada. Brattstrom
(1955:152) has recorded the species from the lower Pleistocene of
southeastern Arizona (Curtis Ranch), bearing out the idea that the
racer has partly withdrawn from a range formerly occupied in the
Southwest at a time when cooler and moister climate prevailed. Other
fossil occurrences are of late Pleistocene age--Vero Beach and
Seminole, Florida (Brattstrom, 1953a:245) and, doubtfully, Rancho
LaBrea, California (Brattstrom, 1953b:376). The range of _mormon_ has
been mapped (Wright and Wright, 1949:134) as extending east to
south-central Montana on the basis of one specimen allocated on the
basis of two characters. Otherwise the range of _mormon_ seems to be
entirely west of the Continental Divide, well separated from that of
_flaviventris_ by desert and mountain barriers. The conspecificity of
_mormon_ with the other subspecies needs to be more thoroughly
investigated, and geographic variation within _mormon_ also merits
study.