Historical population figures are unknown. In 1862, the population was estimated at about 10,000. In 1960, the entire population was about 15,000. In July 2011, the number of island residents was estimated to number about 72,191. Over two-thirds of the population live in the capital, Majuro and Ebeye, the secondary urban center, located in Kwajalein Atoll. This excludes many who have relocated elsewhere, primarily to the United States. The Compact of Free Association allows them to freely relocate to the United States and obtain work there. A large concentration of about 4,300 Marshall Islanders have relocated to Springdale, Arkansas, the largest population concentration of natives outside their island home.