The number of subspecies recognized in Hirundo pyrrhonota Vieillot (Cliff Swallow) from Alaska, Canada, and the northern contiguous United States ranges from one (Peters 1960) to three (e.g., Jewett et al. 1953, Oberholser 1974). Most sources (e.g., American Ornithologists’ Union [A.O.U.] 1957, Behle 1976) recognize two subspecies: hypopolia Oberholser, 1920, breeding from central Alaska to the central Great Basin, and two disjunct populations of nominate pyrrhonota, breeding on the west coast and east of the Rocky Mountains. Although various authors have reported measurements of wing chord, they have not provided quantitative data for other plumage characters, and they disagree in the characterizations and ranges of the subspecies they recognize. Because of this, I reviewed the geographic variation among the northern populations.