Fort Shafter Fort Shafter is in Honolulu CDP , City and County of Honolulu , Hawai ‘ i , extending up the interfluve ( ridgeline ) between Kalihi and Moanalua valleys , as well as onto the coastal plain ( as Shafter Flats ) at Māpunapuna . Fort Shafter is the headquarters of the United States Army Pacific , commanding most Army forces in the Asia - Pacific region with the exception of Korea . A portion of the area is also known as the Palm Circle Historic District and is listed on the National Register of Historic Places , and has been further designated as a U . S . National Historic Landmark . It is also known as Palm Circle or 100 Area . Palm Circle covers a secret underground command center . History . Fort Shafter is the oldest military base on Oahu and celebrated its 100th birthday on June 22 , 2007 . Fort Shafter has been home to the senior Army headquarters in Hawaii for a century . Construction began in 1905 on the ahupua ' a of Kahauiki , former Hawaiian crown lands that were ceded to the United States government after annexation . When the post opened in 1907 , it was named for Major General William Rufus Shafter ( 1835 – 1906 ) , who led the United States expedition to Cuba in 1898 . Palm Circle ( which is a National Historic Landmark ) was laid out as a cantonment for an infantry battalion . The barracks and officers ' quarters were arranged around a parade field ringed by Royal Palm s . The 2d Battalion , 20th Infantry Regiment was the first unit stationed at the new post . Fort Shafter gradually spread out from Palm Circle . Tripler General Hospital once stood where the highway intersection is today ( the hospital moved to its present location in 1948 ) . In 1914 , a regimental - sized cantonment area was constructed ( near Richardson Theater ) . The Hawaiian Ordnance Depot was built in 1917 as a separate post ( near today ' s post exchange ) . In 1921 , the Hawaiian Department moved to Fort Shafter from downtown Honolulu . Finally , a new area was constructed in 1940 for Signal Corps elements . War came to Fort Shafter on December 7 , 1941 , where the Hawaiian Department commander , Lieutenant General Walter C . Short , occupied Quarters 5 . One soldier , Corporal Arthur A . Favreau , 64th Coast Artillery ( Anti - Aircraft ) , was killed on post by an errant Navy shell . Fort Shafter became a busy headquarters and the barracks on Palm Circle were converted to offices . The major headquarters was named successively U . S . Army Forces , Central Pacific Area ( 1943 – 44 ) ; U . S . Army Forces , Pacific Ocean Areas ( 1944 – 45 ) ; and U . S . Army Forces , Middle Pacific ( 1945 – 47 ) . In 1944 , the Army Corps of Engineers erected the " Pineapple Pentagon " ( buildings T - 100 , T - 101 , and T - 102 ) in just 49 days . Two large fishponds were filled in to form Shafter Flats . For most of the next half century , Fort Shafter has remained the senior Army headquarters for the Asia - Pacific region . In 1947 , the headquarters was renamed U . S . Army , Pacific . The post continued to adapt to meet the Army ' s evolving requirements . In the early 1960s the new Moanalua Freeway split the post in two . In 1974 , when the headquarters was eliminated , Fort Shafter became home to U . S . Army Support Command , Hawaii , and the U . S . Army Corps of Engineers , Pacific Ocean Division ( relocated from Fort Armstrong , ( Hawaii ) ) . In 1979 , the Army established U . S . Army Western Command , which was renamed U . S . Army , Pacific in 1990 . In 1983 , the Army conveyed to the State of Hawaii of undeveloped land on the northern end of post . Today Fort Shafter remains the focal point for command , control , and support of Army forces in the Asia - Pacific region .