Until January 2006, the MLO main office was located in the historic Federal Building in downtown Hilo (154 Waianuenue Avenue). This location provided office space for the staff, repair and maintenance laboratories, data processing and analysis facilities, administrative and communications centers for MLO operations. The Hilo office network was connected to the mountain observatory network through a dedicated Internet connection encompassing in excess of 30 computers.
The Hilo Federal Building, constructed in the 1930's, has high interior ceilings and beautiful stonework and solid wooden doors. The views from the office windows are generally of a park or cloud shrouded Mauna Loa and Mauna Kea mountains. The central courtyard of the building has a fountain spouting water from frogs' mouths.