The East Region of San Diego County is the second largest geographical area in the county. It is one of two regions that share an international border with Mexico, and the only region in the county to share a boundary with another county and country. East Region is a very diverse geographic region in the county, and includes vast valleys, arid landscapes, and mountainous terrain. The East Region has a population of over 471,000 residents and is comprised of incorporated and unincorporated areas, suburban and rural communities, and Indian reservations. The communities of El Cajon, Lemon Grove, Alpine, Spring Valley and Mountain Empire all make up a portion East Region.