author
Known chiefly through a late-19th-century military history, this little-documented writer appears as one of several contributors who helped preserve the story of California’s Company B, First Regiment Infantry. The surviving record is thin, but the work remains a useful snapshot of citizen-soldier life in the 1890s.

by California. Infantry. First Regiment. Company B, Irving B. Cook, George Filmer, W. J. Hayes, A. McCulloch, William D. O'Brien
A. McCulloch is a scarce figure in the historical record. The clearest confirmed reference available today is as a named contributor to The "City Guard": A History of Company "B" First Regiment Infantry, N. G. C. During the Sacramento Campaign, July 3 to 26, 1894, a book published in 1895.
Library and public-domain records list A. McCulloch alongside George Filmer, W. J. Hayes, William D. O'Brien, and Irving B. Cook as contributors to that volume. A digitized copy also notes that, after the company's Sacramento campaign, a history committee was appointed, including Corporal A. McCulloch, to gather material and prepare it in readable form.
Beyond that book, I couldn't confirm reliable biographical details such as a full first name, birth and death dates, or a broader bibliography. Because the record is so limited, it is safest to remember A. McCulloch as a contributor to an important regimental history rather than to claim a fuller life story than the sources support.