Johansen was appointed in 1970 by Governor Tom McCall to the professional consulting committee for Oregon's historic preservation program. She also served on the board of directors of the Oregon Historical Society from 1955 to 1965 and was the first woman president of the Pacific Coast Branch of the American Historical Society. She was much in demand as a public speaker for many years.
In 1958 Johansen began work on a history of Reed College. Her research, financed by a Ford Foundation grant, led her to adopt the arduous task of organizing Reed's scattered papers into a coherent archival system. Beginning unofficially in 1960, Johansen became Reed's official archivist from the time of her retirement from active teaching, in 1969, until 1984.
Among the honors Johansen received from Reed are the alumni association's Foster-Scholz Club distinguished service award and an honorary degree of Doctor of Humane Letters. She was noted for her freshman orientation speech, which she delivered for many years. A Reed scholarship was created in her name in 1971. Other external awards she received include a fellowship from the Fund for the Advancement of Education, a Ford Fellowship for study of American historiography, and a distinguished service award from the University of Oregon.
Throughout her 50 years at Reed, in roles as student, teacher and researcher, Johansen's enthusiastic support of Reed education never flagged. "Reed was born during a crisis when the function of a college was in question," she explained in a lecture to the Reed alumni association. "Reed found an answer to that question at that time. . . . Reed is a place for a `free spirit and inquiring mind'; if that dedication prevails, we don't have to worry about the college."