Japan consists of four major islands (which are home to over 90% of Japan's 123 million residents), the Rykyu Islands, and hundreds of smaller islands, mostly uninhabited. The four major islands are Hokkaido, Honshu, Kyushu, and Shikoku. Iwakuni is located on the south-eastern tip of Honshu, the most populous island of Japan. MCAS and the surrounding city of Iwakuni occupy an area which was originally two small towns and three villages. Since Iwakuni was the larger town, with a significant history dating to at least the 17th century, the five communities were incorporated into the city of Iwakuni in 1940. Today, Iwakuni's population is about 113,000.
(Source: This information came directly from the MilitaryHOMEFRONT Installation Overview)
Iwakuni lies at the eastern end of Yamaguchi Prefecture. Its southeastern part faces the Inland Seto Sea and its northern part adjoins Otake City in Hiroshima Prefecture. The city is backed by mountains and its front borders the Seto Inland Sea for a distance of some 1.3 kilometers. Iwakuni is located 300 miles West of Osaka and 30 miles from Hiroshima. Tokyo is 600 miles East of Iwakuni. Iwakuni is in time Zone I, Zulu plus nine hours (i.e., 14 hours ahead of Eastern Standard Time, see "Time Zones"). Subtract one hour during day-light savings time.
(Source: This information came directly from the Military.com Installation Guide)
By popular request, here is a close-up map with Iwakuni's location, showing nearby cities. Iwakuni is located to the right of the word "Yamaguchi." For reference, here is a map of all of Japan, roughly showing Iwakuni's location with a red star. If you have trouble finding the star, follow the white line from the box with the text "IWAKUNI" in it. It is difficult to see, with all of the colors in this map.
(Map sources: Microsoft MapPoint, InfoPlease).