An amalgamation of pre-existing trolley lines (horse-drawn, cable, and electric) laid down by previous trolley companies, the Portland Rail Light & Power Co. Depot-Morrison Line's immediate predecessor was the City & Suburban Railway's "M" Line (Morrison), established in 1892. Sections of the line also included track laid by the Transcontinental Street Railway Co. in 1883 for horse-drawn trolley cars and cable-car tracks set down by Portland Cable Railway in 1890.
Morrison-Depot No. 632 at 5th & Morrison,
As the 1905 Lewis and Clark Exposition drew closer, both the City & Suburban and Portland Railway Companies (both of which would merge in 1904 before the Expo began anyways) girded themselves for the expected onslaught of visitors to Portland (despite the name, the Lewis & Clark Expo was that year's one and only world's fair). The Depot-Morrison was the City & Suburban's direct feed to the gates of the expo (at N.W. 25th & Upshur), and stairs were built at the stops along the line for ease of access.
The line continued under the eventual administration of the PRL&P Co. in 1906, until 1923, when it was folded into Willamette Heights Line.