Cummins, George Wyckoff. History of Warren County New Jersey. N.Y.: Lewis Historical Publishing Company, 1911.
This source gives historical information for the towns and townships of Warren County. It has a name index. There is a more comprehensive name and place index online.
Shampanore, Frank. History and Directory of Warren County, New Jersey. Washington, N.J.: Shampanore & Sons, 1929.
Shampanore refers to this book as a pictorial history of Warren County, but there is some text included. Approximately one-third of the book is a city directory, but for some reason, it does not include Phillipsburg. There is no index.
Snell, James P. History of Sussex and Warren Counties, New Jersey. Philadelphia: Everts and Peck, 1881.
This is a good place to start if you are looking for names. While it gives a good history of Warren County and its townships, its strong points for genealogical purposes are its hundreds of biographical sketches and its good name index. In addition, for each town and township Snell gives the names of various officials, churches, cemeteries, societies, and some businesses.
200 Years of Hope, New Jersey, 1769-1969. Hope, N.J.: Blairstown Press, 1968.
Alpha, 1911-1941. Phillipsburg, N.J.: Thirteenth Anniversary General Committee, 1941.
Background of the Township of Independence, Warren County, New Jersey. Independence Township, N.J.: Bicentennial Committee, 1976.
Franklin Township Bicentennial History, 1776-1976. Washington, N.J.: Hicks Printing Company, 1976.
Harmony Township One Hundred Twenty-Fifth Anniversary, 1839-1964. Citizens Committee of Harmony Township, 1964.
Hicks, Roger. Life in Belvidere: A History of Belvidere New Jersey and the Belvidere Ambulance Corps. Belvidere, N.J.: Belvidere Ambulance Corps, 1970.
Highlights of the Historical Yesteryears of Beattystown: Bicentennial Celebration, July 4, 1976. Hackettstown: Beattystown Presbyterian Church, 1976.
The History of Broadway Written by Grades 5, 6, 7, and 8, 1942 and 1943 under Direction of Teacher, Mrs. Robert C. Haas.
History of Mansfield Township, 1754-1964. Washington, N.J.: Hicks Printing Company, 1964.
Lemasters, Raymond A. Hackettstown, New Jersey: Growing in America. Washington, N.J.: Hicks Printing Company, 1976.
Phillipsburg, New Jersey, Charter Jubilee 1861-1911. Phillipsburg, N.J.: Free Press, 1961 (reprint).
Phillipsburg, New Jersey, Diamond Jubilee 1861-1936. Phillipsburg, N.J., 1936.
Pohatcong, the Prologue: a History of the People of Pohatcong. Pohatcong Heritage Commission, 1981.
Seip, Derson. Oxford: 1912-1917. c. 1976.
Stewart, Florence K. The Belvidere I Remember. c. 1949.
Through the Years: Stewartsville and Surrounding Areas. Greenwich Township Historical Society, [1987?].
Washington, N.J. Centennial Book Committee. Washington New Jersey Centennial History and Program. 1868-1968. United States: Sheridan Printing Company, 1968.White Township History from the Days of the Indian to the Present 1664-1964. c. 1964?