Hawaii is a unique U.S. island state located about 2,000 miles (3,200 km) southwest of the mainland, consisting of 137 volcanic islands and the only state south of the Tropic of Cancer, with a tropical climate and the fourth-longest coastline in the U.S. Its population is concentrated on Oʻahu, home to the capital Honolulu, and it is the most diverse state in the nation—featuring an Asian American plurality, the largest Buddhist community, and a high proportion of multiracial residents, blending Native Hawaiian, North American, and East Asian cultures. Settled by Polynesians between 1000 and 1200 CE, the islands became a unified kingdom in 1810, but after British explorer James Cook arrived in 1778, introduced diseases decimated the Native Hawaiian population; the monarchy was overthrown in 1893, leading to U.S. annexation in 1898. The infamous Japanese attack on December 7, 1941, at Pearl Harbor brought Hawaii global significance, and it became the 50th state on August 21, 1959, though the U.S. formally apologized for the overthrow in 1993, fueling an ongoing Hawaiian sovereignty movement. Today, Hawaii's economy has shifted from a plantation era to thriving on tourism and military defense, while still exporting agricultural goods thanks to its fertile, tropical soil, and its stunning natural scenery, beaches, and surf attract millions of visitors and scientists each year.