Arbustrum Americanum, pp. 135-136 (1785)
Humphry Marshall

3. ROSA humilis. Dwarf Pennsylvanian Rose.
This rises with several slender stems to the height of two or three feet; covered with a brownish green bark, and armed with a few sharp spines. The leaves are composed of three or four pair of lobes, and an odd one, of an oblong egg-shape and sharply sawed on their edges. The leaves of the flower cup have often linear, leafy elongations. The flowers are single and of a pale reddish colour.

According to the USDA Plants database, Rosa carolina L. has two recognized subspecies:
Rosa carolina L. var. carolina and Rosa carolina L. var. setigera Crép.

The latter subspecies is distinct from Rosa setigera and has a very small native range in the U.S. (Maine, New Hampshire & Vermont). The range may extend into eastern Canada; the USDA Plants maps do sometimes include plant ranges for Canada, but perhaps not consistently?

ITIS (Integrated Taxonomic Information System) gives as subspecies for Rosa carolina L.: Rosa carolina ssp. carolina L. and Rosa carolina ssp. subserrulata (Rydb.) W.H. Lewis. The latter subspecies is considered to be synonymous with Rosa carolina var. setigera Crép. Other synonyms are Rosa X rudiuscula Greene (pro sp.), Rosa palmeri Rydb., Rosa subserrulata Rydb. and Rosa texarkana Rydb.
Source: http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=24808
http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=837334