Waipio () is a census-designated place (CDP) located in the Ewa District of the island of Oahu in the City & County of Honolulu, Hawaii, United States. In Hawaiian, wai pio means "curved water". As of the 2020 census, the CDP had a population of 12,082. The U.S. ZIP Code for Waipio is 96797. History In ancient Hawaii, the Battle of Kīpapa Gulch was said to have taken place at Kīpapa Gulch in Waipio. Maʻilikākahi was the mōī of Oahu at the time. The battle began at Waikakalaua Gulch in the adjacent ahupuaa of Waikele. It eventually made its way into Kīpapa Gulch. The raiding party was defeated, and it is said that the gulch was "paved with the corpses of the slain." Geography Waipi'o is located at (21.418050, -157.997988), south of Mililani Town via either Interstate H-2 or Kamehameha Highway (Hawaii Route 99). The town is immediately east of Waikele, separated by Kamehameha Highway, the road that leads southward to Farrington Highway (Hawaii Route 90) with connections then to Pearl City to the east and Waipahu to the west. In this same area south of Waipi'o is the interchange between Hawai'i Interstates H-1 and H-2 at Waiawa. Neighborhoods include Crestview. According to the United States Census Bureau, the CDP has a total area of , all of it land. Demographics As of the census of 2000, there were 11,672 people, 3,974 households, and 2,873 families residing in the CDP. The population density was . There were 4,110 housing units at an average density of . The racial makeup of the CDP was 14.42% White, 2.82% African American, 0.18% Native American, 54.66% Asian, 5.45% Pacific Islander, 0.86% from other races, and 21.62% from two or more races. Hispanic or Latino of any race were 6.76% of the population. There were 3,974 households, out of which 38.6% had children under the age of 18 living with them, 57.1% were married couples living together, 10.5% had a female householder with no husband present, and 27.7% were non-families. 20.9% of all households were made up of individuals, and 2.2% had someone living alone who was 65 years of age or older. The average household size was 2.92 and the average family size was 3.41. In the CDP the population was spread out, with 26.2% under the age of 18, 9.3% from 18 to 24, 34.6% from 25 to 44, 23.4% from 45 to