Birkner's scholarship has focused on aspects of 19th- and 20th-century America: political, urban, oral and biographical history. He has most recently written about the presidency of Dwight D. Eisenhower, with special interest in the role of his Chief of Staff Sherman Adams. He has also written a book on James Buchanan, the only Pennsylvania-born American president, and an award-winning book titled A Country Place No More: The Transformation of Bergenfield, N.J., 1894-1994, which traced the development of that town from small community to a major suburb of New York City.
Birkner received his bachelor's degree from Gettysburg College and his master's degree and doctorate from the University of Virginia in American history with a specialization in Jacksonian politics. He covered the 1988 presidential primary in New Hampshire for the Concord Monitor, where he served as editorial page editor for two years. He regularly contributes op-eds to that paper and other major dailies.