Chicago, Ottawa and Peoria Railway

The Chicago, Ottawa and Peoria Railway, or CO&P, was an electric interurban railway running along the Illinois River Valley between Joliet and Princeton. It was one of the longest lines in the state and was unique as an isolated section of the Illinois Traction System. Intended to be a part of the planned Chicago-Peoria-St. Louis system, the section between the CO&P at Streator and the ITS at Mackinaw Junction was never built, leaving the former line separate from the rest of the ITS. The CO&P provided regular service to the cities along the Illinois Valley until its failure at the height of the Great Depression.

The CO&P was constructed in several different sections. The first segment, from Ladd through Peru and LaSalle to Ottawa, was constructed in 1904, with an extension from Ottawa east to Marseilles completed later that year. Two years later the line was extended in both directions, west from Marquette to Princeton and east from Marseilles to Seneca. Construction continued eastward, the route reaching Morris in 1909 and Joliet in 1912, where it connected with the Chicago and Joliet Electric Railway. A branch to Streator was built in 1908.

In 1923 the CO&P became the Illinois Valley Division of the Illinois Traction System, and beginning in 1924 the rolling stock used was modernized from heavy wooden combines to lightweight steel coaches. The line was lightly built and never carried much freight, depending almost entirely on passenger service. Service out of Joliet was hourly with alternating trains west of Spring Valley terminating at Princeton and Ladd, plus two-hour service to Streator.

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