Currently Okinawa contains 75% of the American military bases in Japan despite consisting of only 0.6% of Japan’s total land area. Due to the large concentration of bases, nearly 20% of the land in Okinawa Island is used by the American military, such as Futenma and Kadena Air Base.

The reason for the numerous bases on the tiny island of Okinawa, stem from the San Francisco Peace Treaty of 1951, in which the Ryukyu Islands became an American territory administered by the United States. Although control over the islands was reverted back to Japan in 1972, the bases continue to remain despite widespread opposition. Numerous protests in regards to the base continue to occur in Okinawa due to issues relating to ownership of the land, proper compensation, pollution stemming from the base, criminal acts committed by American servicemen, as well as other issues.

Further Reading:
Okinawa Prefectural Site on US military presence in Okinawa
Clickable US military base on Okinawa map