"January 3, 1938: "Hobson bridge near prison annex out with piers undermined. This road closed and impossible to make repairs as yet."(Daily Capital Journal)"
"June 25, 1940: "The Marion county court yesterday ordered closing of the Hobson bridge located two miles northeast of the penitentiary annex pending a decision on whether to repair the structure or rebuild it entirely. It is chiefly used for hauling of hay across Mill creek." (Statesman Journal)"
"August 10, 1941: "Near the penitentiary annex and built across Mill creek is the Hobson bridge. Constructed in the early 1890's, the structure was on a main trade route from the surrounding hills to Salem. Early settlers used this route to come to Salem for their shopping and to catch the river steamer to Portland. Today, condemned, it is in the heart of a 'lovers' lane.'" (Statesman Journal)"
"Mill Creek Correctional Facility (MCCF) - In 1929, the former State Training School in Salem was turned over to the Penitentiary for use as a subsidiary minimum security prison, called the Annex Farm (later renamed Mill Creek Correctional Facility)."
Narrowing down possible location across Mill Creek - somewhere between the unnamed bridge in Cascades Gateway Park and Kuebler Blvd.
3 items from https://oregoncoveredbridges.weebly.com/hobson.html
"January 3, 1938: "Hobson bridge near prison annex out with piers undermined. This road closed and impossible to make repairs as yet."(Daily Capital Journal)"
"June 25, 1940: "The Marion county court yesterday ordered closing of the Hobson bridge located two miles northeast of the penitentiary annex pending a decision on whether to repair the structure or rebuild it entirely. It is chiefly used for hauling of hay across Mill creek." (Statesman Journal)"
"August 10, 1941: "Near the penitentiary annex and built across Mill creek is the Hobson bridge. Constructed in the early 1890's, the structure was on a main trade route from the surrounding hills to Salem. Early settlers used this route to come to Salem for their shopping and to catch the river steamer to Portland. Today, condemned, it is in the heart of a 'lovers' lane.'" (Statesman Journal)"
Page 7 of http://records.sos.state.or.us/ORSOSWebDrawer/RecordView/728...
"Mill Creek Correctional Facility (MCCF) - In 1929, the former State Training School in Salem was turned over to the Penitentiary for use as a subsidiary minimum security prison, called the Annex Farm (later renamed Mill Creek Correctional Facility)."