From the Opinion Journal:
I don’t think there’s a good word for what Mr. Hall did: “researcher” is too dry, “historical investigator” carries hints of melodrama, and “archivist” suggests a dutiful drudge, which Mr. Hall was not. “Amateur historian” probably fits best, though it sounds vaguely derivative and second-tier. Following a career with the Labor Department–he retired in the early 1970s–Mr. Hall turned himself into the world’s foremost authority on the assassination of Abraham Lincoln. Historians, pros and amateurs alike, sought him out for his knowledge and access to his exhaustive files. As one of them put it, James O. Hall knew more about Lincoln’s murder than anyone who ever lived, including John Wilkes Booth.
Uncorrupted by graduate degrees, with no thought of professional advancement, Mr. Hall exemplified a tradition in the study of American history, particularly in the Lincoln field, where the most interesting writing and research is often done by hobbyists. It’s been this way from the beginning. Until the middle of the last century, all the great Lincoln biographers made their livings outside the university–journalists like Ida Tarbell and free-lance enthusiasts like Benjamin Thomas produced biographies that were beautifully written and filled with news. Even now, dozens of Lincoln or Civil War roundtables flourish, and many of them publish quirky newsletters in which members let drop bits of recondite research or boldly advance new theories. While other areas of academic research have shriveled into hyperspecialization, the amateur tradition has kept the Lincoln field blessedly free of the guild mentality that can make academic history seem the dreary province of pedants and bullies.