Described in 1910 from California, Colorado, New Mexico, Oregon, and Utah, Leptoglossus clypealis Heidemann was known as far east as eastern Missouri by the early 1940s; it was recorded only recently east of the Mississippi River (Illinois). Based mainly on images posted on BugGuide, its eastern North American range can be extended in the United States to New Jersey, Virginia, and North Carolina; an Ontario record is the first for Canada. Additional new state records and new localities in previously recorded states are presented. The eastward spread of L. clypealis is compared with that of a congener, L. occidentalis Heidemann. As a strong flier, L. clypealis might have undergone a gradual eastward spread, but the extensive planting of eastern redcedar (Juniperus virginiana L.) for shelterbelts in the Great Plains during the 1930s might have triggered increases in the coreid's population densities, enhancing the probability of further eastern spread. Long-distance dispersal aided by winds and transport via cargo and motor vehicles might also have been involved in its recent range expansion. Nymphs of L. clypealis were observed on five species of the coniferous genus Juniperus (54 sites), mainly on fruitbearing trees of J. scopulorum Sarg. and J. virginiana; adults were collected on two additional species of juniper at five sites. The coreid was found on a eudicot, the anacardiaceous shrub Rhus aromatica Aiton at three sites.