The Hunterdon County Historical Society is an excellent source of information on the history of Hunterdon County. As stated on the website, "The mission of the Hunterdon County Historical Society is to collect, preserve and share the evolving social and material history of the entire County of Hunterdon, New Jersey. The Society will fulfill its mission through educational programs, research and publications, and by maintaining for public benefit the growing collections of the Society and the buildings that house them: The HCHS Archives, the Hiram E. Deats Memorial Library and the 1845 Doric House Museum.
The official Hunterdon County website has an extensive writeup on the county's history, including the evolution of county government, complete minutes of meetings, the stories of the courthouse and jail, and the historic Bruno Haptmann trial for the fatal kidnapping of the son of Colonel Charles Lindbergh.
Another superb historical source is Goodspeed Histories, a website devoted to New Jersey History and Genealogy. The website and blog are run by Marfy Goodspeed, who has researched Hunterdon County families since 1981 when she started her house history business.