Harahan was named in honor of James Theodore Harahan, president of the Illinois Central Railroad from 1906-1911. The Illinois Central track runs parallel to Airline Highway.
On February 17 2006, the Harahan police department was given a grade F by The Police Complaint Center, a national organization against police misconduct. The complaint telephone call which they believe warrants this grade can be heard here
Harahan is located at (29.941085, -90.202020) and has an elevation of . According to the United States Census Bureau, the city has a total area of 2.5 square miles (6.3 km²), of which, 2.0 square miles (5.1 km²) of it is land and 0.5 square miles (1.2 km²) of it (19.59%) is water.
There were 3,994 households out of which 28.2% had children under the age of 18 living with them, 55.2% were married couples living together, 11.1% had a female householder with no husband present, and 29.9% were non-families. 25.3% of all households were made up of individuals and 11.4% had someone living alone who was 65 years of age or older. The average household size was 2.42 and the average family size was 2.91.
In the city the population was spread out with 20.8% under the age of 18, 6.9% from 18 to 24, 28.5% from 25 to 44, 24.0% from 45 to 64, and 19.8% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 90.1 males. For every 100 females age 18 and over, there were 86.9 males.
The median income for a household in the city was $44,702, and the median income for a family was $55,319. Males had a median income of $37,995 versus $27,921 for females. The per capita income for the city was $23,448. 4.7% of the population and 3.1% of families were below the poverty line. 3.7% of those under the age of 18 and 8.2% of those 65 and older were living below the poverty line.
Harahan is home to Colonial Golf and Country Club, one of only three golf courses located in East Jefferson (the East Bank of Jefferson Parish).