An entrance to the Medical Center station on the new line was located on Paulina Street, a block west of Marshfield Avenue.

The Metropolitan West Side Elevated Railroad Company was granted a 50-year franchise by the Chicago City Council on April 7, 1892,[2] and began securing right-of-way shortly thereafter.

[2] Originally intending for its railroad to be powered by steam locomotives like the competing South Side and Lake Street Elevateds, the Metropolitan decided in May 1894 to use electric traction instead.

[8] The tracks had already been largely constructed prior to the decision to electrify them, but retrofitting the third rail proved an easy task besides the switches of the main line.

[10] The main line and Logan Square branch up to Robey[c] had their tracks completed by the middle of October 1894, and were given power in April 1895 for test and inspection runs.

The similarly-named Metropolitan West Side Elevated Railway Company was organized in January 1899 and assumed operations on February 3 of that year.

[17] Having gone bankrupt in 1919 due to rising inflation from World War I and state regulations, the AE&C was split into two parts, one of which was the Chicago Aurora and Elgin Railroad (CA&E), in 1921.

[28] Work on the subway was delayed by World War II; it finally opened on February 25, 1951, rerouting Logan Square and Humboldt Park trains from Marshfield Junction.

[1] As construction progressed, Garfield trains were rerouted from the "L" structure to temporary at-grade trackage running directly on Van Buren Street between Kedzie and Halsted, ceasing to make intermediate stops in that area; this included the main line stations of Marshfield and Racine.

[32] The CA&E, having long struggled financially, had serious doubts about its ability to reroute its right-of-way into the new expressway median, and more immediately refused to use the at-grade tracks due to safety concerns as well as the prospect of delays caused by the use of traffic signals at road crossings.

[32] Douglas Park trains started using the Paulina Connector – the old Logan Square structure, connected to the Lake Street Elevated – to get to the Loop on April 4, 1954, removing the last traffic to Marshfield and Racine; they were demolished soon afterwards.

[46] As early as 1934, several morning rush hour CA&E trains a day stopped at Laflin instead of Marshfield to discharge eastbound passengers.

[49] Unlike other elevated railroads at the time, the Metropolitan did not sell tickets for passengers to present to staff; instead customers gave their fare to the station agent to record in a registry, a practice similar to streetcars.

[48] By the 1940s, the neighborhood was inhabited by people of African, Greek, Italian, Jewish, and Mexican ancestry; it was considered blighted by officials and the public, but residents contested that description.

[51] By the early- to mid-20th century, this route was one of the "Big Five" streetcar lines in Chicago, which had the highest ridership, received the most amenities, and had the shortest wait times.

[52] Another streetcar route ran on Van Buren Street adjacent to the Metropolitan's tracks, being powered by horse until it was electrified in 1896.

[59] In the last full year of its operation, 1953, Marshfield served 688,433 passengers on the "L", a 3.48 percent decline from the 713,264 of 1951; ridership statistics are unavailable throughout the entire "L" for 1952.

[60] For 1953, Marshfield was in the exact middle of the main line's ridership, surpassing Racine and Franklin/Van Buren but underperforming Canal and Halsted.

[e][65] These statistics only measured the number of passengers who originated a trip from Marshfield rather than used it as a transfer, so are likely underestimates of the true patronage of the station.

[f] After the September 1953 suspension of direct "one-seat ride" service into Chicago, the railroad lost half of these riders by December as riders opted instead for the nearby Chicago and North Western Railroad (C&NW, modern-day Union Pacific West Line) or automobiles to get into the city.