Sayornis phoebe (Eastern Phoebe) has expanded its breeding range southeasterly at water-based anthropogenic structures along forested streams in the Pee Dee region of South Carolina. Its current range is truncated in the Upper Coastal Plain, 31–35 km below the lower boundary of the Sandhills subregion (Orangeburg Scarp). The predominance in the Upper Coastal Plain of South Carolina of structures that are less suitable for nesting by Eastern Phoebes (e.g., small bridges without ledges, box culverts), in contrast to preferred structures (i.e., small bridges with ledges) available upriver in the Sandhills and eastern Piedmont of North Carolina, has not limited their colonization (∼2 km y^-1 since ca. 1990). This breeding-range expansion is consistent with a correlative ecological-niche model (ENM) prediction that the Eastern Phoebe is expanding its breeding range in the Pee Dee region across a broad front toward the SC coast. This breeding-range expansion, with a slight drop in latitude and elevation, has been slower than the contemporary expansion of Petrochelidon pyrrhonota (Cliff Swallow) in the same direction in the same region. Hirundo rustica (Barn Swallow) uses water-based anthropogenic structures, but has also widely colonized land-based structures during its faster past breeding range-expansion into the Pee Dee region. Differences in the number, size, and suitability of water-based anthropogenic structures used by these 3 species suggest additional constraints that influence the colonization rate and population size of Eastern Phoebes.