The U.S. Army Museum of Hawaii is located in Battery Randolph at the Fort DeRussy Military Reservation on Oahu, Hawaii.
It's located in a fairly strange place for a museum, on a very expensive location, next to resorts and hotels in the Waikiki neighborhood of Hawaii. The oddity lies in the nature of the building itself.
It was constructed 1911 as a shore battery, complete with some rather large guns, to protect the shoreline and nearby harbors from naval attack. Thus, it was designed and built to withstand direct fire from other, rather large, guns. In 1970, the other battery (Battery Dudley) was successfully demolished, but the wrecking ball was entirely ineffective on Battery Randolph. The demolition company contracted for the job was bankrupted by the endeavor. The estimated quantity of explosives required to damage the building to the extent that it could be demolished would supposed shatter every window in Waikiki and seriously damage several adjacent resorts. So rather the land opening up to development, it's now a park and the stubborn building was turned into a museum in 1976.
The museum collection covers a broad swath of time, very specifically focusing on the military in Hawaii and Hawaiians in the military. It starts with Hawaiian warfare, complete with a collection of traditional Hawaiian weapons. It covers the history and intended use of the battery, followed by exhibits on WWII, Korea, and Vietnam. Of particular note is an exhibit focusing on the service of Hawaiian Japanese Americans during WWII. It has an extensive exhibit on General Eric K. Shinseki, complete with a variety of personal effects. That's followed by The Gallery Of Heroes, an exhibit honoring Hawaiians that have received Medals of Honor, Distinguished Service Crosses, etc.
On an island with the USS Arizona Memorial, the Battleship Missouri Memorial, the Pacific Aviation Museum, etc. this is not necessarily the most essential museum to check out. That said, it's an interesting place to spend a few hours.