Hilo is the largest settlement in and the county seat of Hawaiʻi County, Hawaii, United States, which encompasses the Island of Hawaii, and …Hilo is the largest settlement in and the county seat of Hawaiʻi County, Hawaii, United States, which encompasses the Island of Hawaii, and is a census-designated place. The population was 44,186 according to the 2020 census. It is the fourth-largest settlement in the state of Hawaii, the largest settlement in the state outside of Oahu, and the largest settlement in the state outside of the Greater Honolulu Area.