The rail company that was destined to become the Chicago, Rock Island, and Pacific Railroad was incorporated in 1847, and construction of its first stretch of track began in 1851 in Illinois between Chicago and Joliet. It continued to grow to the west and to the south, eventually servicing much of the central United States: Chicago, St. Louis, Omaha, Kansas City, and Oklahoma City, with branches into Texas, New Mexico, and other surrounding states. But, like most other railroads in the United States, freight and passenger service began to decline in the second half of the 1900s, and the Rock Island Line ceased operations in 1980.
One of the Rock Island Line's stops was in Lincoln, where it made a long sweeping arc from the southwest corner of the city into downtown before continuing on to the north. Today, two clear reminders of the railroad remain: the old depot building at 20th and O Streets, and the bike trail bearing the rail line's name.
The Rock Island Trail starts out in the north at the Lincoln Children's Zoo, near the intersection of 27th and Capitol Parkway, and is accessible via its connection with the Billy Wolff trail. The trail heads south through the Antelope Park and Memorial Park greenspaces, curving gently to the west as it heads through parks and neighborhoods. After about two and a half miles, the trail intersects with the Helen Boosalis and Tierra Williamsburg trails and crosses over Nebraska Highway. From there, it continues to the southwest through more neighborhoods, eventually ending at Densmore Park soon after crossing Old Cheney Road. At this point, you can turn around and ride the five miles back to your starting point along the same trail, or you can take the SouthPointe trail to the east until it links up with the Tierra Williamsburg trail, which will take you back to the bridge over Nebraska Highway.
Whichever route you take, the Rock Island Trail is a nice 10+ mile out-and-back or semi-loop. You can start planning your route on the Wireless Bike Map.