Johnston is known as the first person to systematize early efforts by Samuel Swett Green, Justin Winsor, and Melvil Dewey to provide informational assistance to library users.
Within the first few years of his teaching, reference work was established in the profession as a formal topic of study.
[3] He continued teaching courses in reference service and bookbinding at the library school until 1905.
[4] A list of reference books used in Johnston's course was published, first in 1899 and then revised in 1903, in the State Library Bulletin.
[1] He taught many of the profession's pioneer figures, including Isadore Gilbert Mudge and Josaphine Adams Rathbone.