The Rock Island Spur is a 47.5-mile trail from Pleasant Hill to Windsor, Missouri, where it joins the Katy Trail. The surface is compacted gravel.
It runs along an abandoned railroad bed that was originally part of the Chicago, Rock Island, and Pacific Railroad, one of the country's largest railroads at its peak. The Rock Island RR line served a wide area of the Midwest, including Illinois, Iowa, Missouri, Arkansas, Kansas, Oklahoma, Texas, and Louisiana.
The Rock Island RR line was known for a popular song, "The Rock Island Line." The song was written in the 1930s and tells the story of a train ride on the Rock Island RR line. The folk singer Leadbelly popularized the song, and has been recorded by many other artists.