On April 1, 1946 a 7.8 magnitude earthquake near the Aleutian Islands created a 14-meter high tsunami that hit Hilo hours later killing 159. As a result an early warning system was established to track these killer waves and provide warning. On May 23, 1960, another tsunami, caused by an 8.6 magnitude earthquake off the coast of Chile the previous day, claimed 61 lives due to failure to heed warning sirens. Low-lying bayfront areas of the city, previously populated, were rededicated as parks and memorials.
Hilo is located at 19°42'20" North, 155°5'9" West (19.705520, -155.085918)1.
According to the United States Census Bureau, the town has a total area of 151.4 km² (58.4 mi²). 140.6 km² (54.3 mi²) of it is land and 10.7 km² (4.2 mi²) of it is water. The total area is 7.10% water.
As of the census of 2000, there are 40,759 people, 14,577 households, and 10,101 families residing in the town. The population density is 289.9/km² (750.8/mi²). There are 16,026 housing units at an average density of 114.0/km² (295.2/mi²). The racial makeup of the town is 17.12% White, 0.45% African American, 0.34% Native American, 38.30% Asian, 13.12% Pacific Islander, 0.94% from other races, and 29.74% from two or more races. 8.78% of the population are Hispanic or Latino of any race.
There are 14,577 households out of which 30.6% have children under the age of 18 living with them, 48.5% are married couples living together, 15.2% have a female householder with no husband present, and 30.7% are non-families. 24.1% of all households are made up of individuals and 10.6% have someone living alone who is 65 years of age or older. The average household size is 2.70 and the average family size is 3.19.
In the town the population is spread out with 24.7% under the age of 18, 10.3% from 18 to 24, 24.4% from 25 to 44, 23.9% from 45 to 64, and 16.7% who are 65 years of age or older. The median age is 39 years. For every 100 females there are 95.9 males. For every 100 females age 18 and over, there are 91.9 males.
The median income for a household in the town is $39,139, and the median income for a family is $48,150. Males have a median income of $36,049 versus $27,626 for females. The per capita income for the town is $18,220. 17.1% of the population and 11.1% of families are below the poverty line. Out of the total people living in poverty, 23.5% are under the age of 18 and 6.7% are 65 or older.