During the summer of 2003, we captured and radiotagged ten male Myotis septentrionalis (northern bats) on the Fernow Experimental Forest (FEF) in the Allegheny Mountains of West Virginia to investigate day-roost selection. Of 16 roosts that were located, 13 were in Robinia pseudoacacia (black locusts), five in snags and eight in live trees. The other three roosts occurred in a Sassafras albidum (sassafras) snag and two live Acer saccharum (sugar maples). All live trees used as roosts were medium to large, canopy-dominant trees with considerable amounts of exfoliating bark and numerous broken limbs and cavities. Snags used as roosts were smaller than trees and other snags in surrounding stands, whereas live trees used as roosts were larger than other trees and snags in surrounding stands. Similar to previous research on female northern bats in the Allegheny Mountains, we observed a strong preference for both live and snag black locust as roosts over other available species. The high abundance of black locust as an important component on the FEF has been a relatively recent development dating to the early 1900s. Use of live canopy-dominant black locust with characteristics of mature forest trees lends support that older forests with decadent conditions provide important day-roost habitat, whereas use of both canopy dominant live trees and long-lasting black locust snags may support the ecological concept of roosting “areas” for northern bats.