April 20, 1826, in a logging camp on the west bank of the Penobscot River in Township No. 2 (about 60 miles upriver from Bangor, Maine).
June 16, 1909, Waltham, Massachusetts.
Jackson Corner Cemetery, Jackson, Maine.
Erastus was the third of 13 children of Cyrus Boardman Johnson and Hepzibah Hunt Page. He married twice, to Ella Alzardia Brown and Mary Pamelia Silsbee.
At age 17, Johnson became a school teacher in Machias, Maine. At 26, he sailed on the Gold Hunter to join some of his brothers in the California Gold Rush; he remained in the San Francisco area for about eight years. Moving to Pittsburgh, Pennsylvania, in 1860, he stayed there 24 years, working in the oil business. He then moved to Jackson, Maine; to Washington state; and lastly to Waltham, Massachusetts.