Port Republic was settled as early as 1637, but a charter was not applied for until founders Evi Smith, Hugh McCullum, and Richard Wescoat applied for a Royal Charter to build a dam, sawmill, and gristmill on their land along Nacote Creek..
In its early days Port Republic was known as Wrangleboro. During the American Revolutionary War, Port Republic provided refuge to the residents of the nearby community of Chestnut Neck when the British Army sacked their town on October 6, 1778. Among the refugees was Daniel Mathis, a tavernkeeper who built the Franklin Inn in Port Republic, which is a private house today. Most memorable revenge that was visited on the British navy was when some ships were trapped in the creek by the ebb tides..
Port Republic was Incorporated as a city by an Act of the New Jersey Legislature on March 1, 1905, from portions of Galloway Township.
As of the census of 2000, there were 1,037 people, 365 households, and 289 families residing in the city. The population density was 136.0 people per square mile (52.5/km²). There were 389 housing units at an average density of 51.0/sq mi (19.7/km²). The racial makeup of the city was 95.08% White, 1.64% African American, 0.39% Native American, 0.58% Asian, 0.00% Pacific Islander, 0.68% from other races, and 1.64% from two or more races. 1.06% of the population were Hispanic or Latino of any race.
There were 365 households out of which 36.7% had children under the age of 18 living with them, 64.9% were married couples living together, 10.1% had a female householder with no husband present, and 20.8% were non-families. 16.7% of all households were made up of individuals and 7.9% had someone living alone who was 65 years of age or older. The average household size was 2.82 and the average family size was 3.17.
In the city the population was spread out with 24.0% under the age of 18, 8.0% from 18 to 24, 26.1% from 25 to 44, 29.9% from 45 to 64, and 12.0% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 96.8 males. For every 100 females age 18 and over, there were 93.1 males.
The median income for a household in the city was $65,833, and the median income for a family was $70,714. Males had a median income of $42,833 versus $34,375 for females. The per capita income for the city was $24,369. 3.5% of the population and 3.2% of families were below the poverty line. Out of the total population, 0.0% of those under the age of 18 and 13.2% of those 65 and older were living below the poverty line.
There are 550 households in the city, 16 of them farms, and only 9 commercial enterprises.
The Garden State Parkway and U.S. Route 9 both pass through Port Republic, as do County Route 575 and County Route 561 Alternate. A small piece of Route 167 is in the city.