Reykjanesbær emerged as a town a few years ago, when two towns and rivals merged into one, Narðvík and Keflavík. For decades, thousands of American military personnel lived on a military base by Keflavík that the United States Army built during WWII. A naval base for Iceland’s defense and to secure the northern Atlantic route. The Army also built an airfield, which later became Iceland’s international airport. The military base was in operation until September 2006. During that time, thousands of U.S. soldiers lived on the base, sometimes with more than 5,000 military and civilian staff and family members. At the same time, a large portion of the town's residents worked on the base. When they left, the former base also merged into the Reykjanesbær municipal.