Califon, NJ. Online Offers. Califon is a borough in Hunterdon County, New Jersey, United States. As of the 2010 United States Census, the borough population was 1,076. The town was to originally be called California, but was shortened to Califon in order to fit on the welcome sign. Alternatively, the name was related to a bright yellow cattle feed sold during the Gold Rush. Califon was a station on the High Bridge Branch of the Central Railroad of New Jersey. The rail line was abandoned in 1976 and now serves as a Hunterdon County-administered rail trail called Columbia Trail, which runs south to High Bridge and north to points in Morris County.