Lakes and reservoirs are rare in Hawai'i, and Wahiawā is at once unique in being surrounded on three sides by Lake Wilson (also known as Wahiawā Reservoir). The town must be accessed by either of two bridges on Kamehameha Highway (State Rte. 80) across the narrow north and south arms of the reservoir. Outside of the reservoir, the town used to be surrounded by military bases and agricultural fields, but development is making its way up from the increasingly urbanized southern portion of the central plain. Still, there are significant U.S. Army facilities here, including Schofield Barracks, Wheeler Army Airfield, and East Range, an Army training area extending into the hills south and east of town. Schofield Barracks alone is larger than Wahiawa.
The U.S. postal code for Wahiawā is 96786
Wahiawā is located at 21°30'9" North, 158°1'23" West (21.502574, -158.022938)1. Vehicular routes heading towards the North Shore from Wahiawa are Kamehameha Highway (State Rte. 80) to Hale'iwa and Kaukonahua Road (State Rte. 801) to Waialua. Wheeler and Schofield are reached along Wilikina Drive (State Rte. 99) from the south bridge, a road that eventually connects to both Kamehameha Highway and Kaukonahua Road northwest of town. Kamehameha Highway continues south (as State Rte. 99) past Wheeler to Mililani Town. However, the Interstate H-2 terminates at Wilikina Drive near the Kamehameha Highway intersection, and is a less congested route southward to Mililani and beyond to Pearl City and Honolulu via Interstate H-1. Kunia Road (State Rte. 750) runs from Wilikini Dr., between Schofield and Wheeler, then southward along the mostly still agricultural western side of the plain to Kunia and Waipahu beyond.
According to the United States Census Bureau, the town has a total area of 6.2 km² (2.4 mi²). 5.5 km² (2.1 mi²) of it is land and 0.7 km² (0.3 mi²) of it is water. The total area is 11.34% water.
As of the 2000 Census there were 16,151 people, 5,376 households, and 3,956 families residing in the town. The population density was 2,955.4/km² (7,642.8/mi²). There were 5,900 housing units at an average density of 1,079.6/km² (2,791.9/mi²). The racial makeup of the town was 11.31% White, 2.02% African American, 0.32% Native American, 45.77% Asian, 9.62% Pacific Islander, 1.83% from other races, and 29.14% from two or more races. 11.00% of the population were Hispanic or Latino of any race.
There were 5,376 households out of which 31.3% had children under the age of 18 living with them, 49.2% were married couples living together, 18.0% had a female householder with no husband present, and 26.4% were non-families. 21.9% of all households were made up of individuals and 10.5% had someone living alone who was 65 years of age or older. The average household size was 2.97 and the average family size was 3.45.
In the town the population was spread out with 26.1% under the age of 18, 8.6% from 18 to 24, 26.6% from 25 to 44, 19.9% from 45 to 64, and 18.8% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 94.6 males. For every 100 females age 18 and over, there were 91.4 males.
The median income for a household in the town was $41,257, and the median income for a family was $46,524. Males had a median income of $32,018 versus $25,287 for females. The per capita income for the town was $16,366. 16.7% of the population and 13.5% of families were below the poverty line. Out of the total people living in poverty, 23.8% were under the age of 18 and 9.9% were 65 or older.