He has been director,[11] then executive director[12][13][14][15] and is currently CEO of The Bronx County Historical Society.[5] He founded and established the Society's The Bronx County Archives and The Bronx County Historical Society Research Library.[4] He is also a Board Member of the Greater Bridgeport Symphony in Bridgeport, Connecticut[16] and as of 2017 was Vice Chairman of the Board of Trustees of the Discovery Museum and Planetarium in Bridgeport.[17]
Publications of the Bronx County Historical Society: 1955–2000. New York: The Bronx County Historical Society, 1999. OCLC42303755
The Study and Writing of History. New York: The Bronx County Historical Society, 2007. ISBN9780941980500.
Books paired with others
The Bronx in the Innocent Years, 1890-1925. The Life in The Bronx Collection. New York: Harper & Row, 1985. Hermalyn and Lloyd Ultan. ISBN9780060154196. Hermalyn was also project editor.
The Beautiful Bronx 1920-1950. The Life in The Bronx Collection. New York: Harmony, 1988. Hermalyn and Ultan. ISBN978-0517548004. Hermalyn was also project editor.
Landmarks of the Bronx. New York: Bronx County Historical Society, 1989. Hermalyn and Robert Kornfeld. OCLC21927704.
The Bronx. It Was Only Yesterday. 1935-1965. The Life in The Bronx Collection. New York: The Bronx County Historical Society, 1992. Hermalyn and Ultan. ISBN9780941980333. Hermalyn was also project editor.
The Bronx Cookbook Plastic Comb – 1997. New York: The Bronx County Historical Society, 1997. Hermalyn and Peter Derrick. ISBN978-0941980371.
The Birth of the Bronx: 1609 - 1900. The Life in The Bronx Collection Vol. 4. New York: The Bronx County Historical Society, 2000. Hermalyn and Ultan. ISBN0-941980-38-3. Hermalyn was also project editor.
Time and the Calendar. New York: History of New York City Project, 2001. Elizabeth Beirne and Hermalyn. ISBN9780965233163.
Yankee Stadium: 1923-2008: Images of Baseball. Mount Pleasant, SC: Arcadia Publishing, 2009. Hermalyn and Anthony C. Greene. ISBN978-1531643256.
The Bronx. Then & Now. Mount Pleasant, SC: Arcadia Publishing, 2010. Kathleen A. McAuley and Hermalyn. ISBN978-0738573151.
A Historical Sketch of the Bronx. New York: The Bronx County Historical Society, 2018. Hermalyn and Ultan. ISBN0-941980-72-3.
Hudson's River. New York: The Bronx County Historical Society, 2020. Hermalyn and Sidney Horenstein. ISBN0-941980-76-6.
Books with editing contributions by Hermalyn (selected)
^St John Kelly, Erin (6 February 1994). "Playing in the Neighborhood". The New York Times. New York City. Retrieved 5 March 2017. Lloyd Ultan and Dr. Gary Hermalyn, two authorities on Bronx history