UP Rock River Bridge (Ashippun)

In 1884, the Princeton & Western Railway (P&W) constructed a 13 mile branch from the existing Chicago, St. Paul, Minneapolis & Omaha Railway (Omaha Road) at Wyeville, Wisconsin to Necedah, Wisconsin.  The railroad soon came under lease of the Chicago & North Western Railway (C&NW).  During the early 20th Century, the C&NW began a program of improvements, constructing new cutoffs and significantly increasingly efficiency over the system, particularly in Wisconsin and northern Illinois.  In 1910, the Milwaukee, Sparta & North Western Railway (MS&NW), a subsidiary of the C&NW, began construction a new cutoff across central Wisconsin.  In 1912, the MS&NW completed 23 miles between Sparta, Wisconsin and Wyeville, Wisconsin; as well as 133 miles between Necedah and Wiscona, a railroad junction on the north side of Milwaukee.  The P&W was sold to the MS&NW in 1912, which was promptly consolidated into the C&NW.  This line provided a better connection for the C&NW through Wisconsin, and avoided the steep grades of the previous mainline from Sparta to Madison.  The line also improved the C&NW connection to the Twin Cities of Minneapolis and St. Paul by way of the C&NW controlled Omaha Road.  The line between Butler, Wisconsin and Clyman Junction, Wisconsin would be double tracked; while the remainder between Clyman Junction and Wyeville was built wide enough for a second track, but no second track was installed.

By the 1920s, the C&NW was operating an expansive railroad network throughout the Midwest, radiating north and west from Chicago.  This line served as one of the principal mainlines of the railroad, connecting Milwaukee to the Twin Cities.  In 1959, much of the second track between Butler and Clyman Junction was removed as operations over the line no longer warranted a second track.  The line remained largely unchanged until March 1973, when a tunnel collapsed at Tunnel City, Wisconsin.  This led to the line being abandoned west of Tunnel City, and a new connection track being constructed to the Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) mainline, which the C&NW would use to reach Winona, Minnesota.  In 1995, the C&NW was purchased by the Union Pacific Railroad, the current owner of this line.  Today, UP operates the Wyeville Subdivision between Wyeville and Adams, Wisconsin; the Adams Subdivision between Adams and Wiscona; and the Winona Subdivision between Wyeville and Tunnel City.  The segment between Tunnel City and Sparta remains abandoned, although much of the infrastructure remains intact.