Ellenwood is an unincorporated community in Clayton, Henry, Rockdale and DeKalb counties in the U.S. state of Georgia. The community is …Ellenwood is an unincorporated community in Clayton, Henry, Rockdale and DeKalb counties in the U.S. state of Georgia. The community is a southeast suburb of Atlanta and is located along Interstate 675 and Georgia State Route 42. With a population of 46,967 and ten constituent neighborhoods, Ellenwood is the 19th largest community in Georgia.