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| Name | CTA Yellow Line - North Shore Channel Bridge |
| Built By | Chicago, North Shore & Milwaukee Railroad Northwestern Elevated Railroad |
| Currently Owned By | Chicago Transit Authority |
| Superstructure Contractor | Hansell-Elcock Company of Chicago, Illinois |
| Substructure Contractor | L.E. Meyers Company of Chicago, Illinois |
| Design Engineer | I.F. Stern of Chicago, Illinois |
| Length | 905 Feet Total, 120 Foot Main Span |
| Width | 2 Tracks |
| Height Above Ground | 50 Feet (Estimated) |
| Superstructure Design | Double Intersection Warren Deck Truss, Pratt Pony Truss, Deck Plate Girder and Concrete Skeleton Abutment |
| Substructure Design | Concrete, Steel Tower and Steel Bent |
| Date Built | 1925 |
| Traffic Count | 120 Trains/Day (Estimated) |
| Current Status | In Use |
| Significance | Regional Significance |
| Documentation Date | 2/26/2023 |
During the early 20th Century, the area immediately north of Chicago saw unprecedented growth. Existing passenger rail service along the existing line Chicago, North Shore & Milwaukee Railroad (CNS&M) line became crowded. In 1924, the CNS&M began purchasing land for a new line between Howard Street and North Chicago, set several miles from the lake shore. This new route was expected to shorten travel times by 20 minutes, and provide a bypass of the congested shore line route. The first portion to Niles Center opened in 1925, and was jointly constructed by the CNS&M and the Northwestern Elevated Railroad. In 1926, the remainder of the route opened for service, featuring a double track electrified railroad in a private right-of-way. Throughout the 1930s, the railroad financed significant grade separation projects, particularly along US-41. However, the railroad ceased operations in 1963. By 1965, large portions of the track has been removed north of Lake-Cook Road. Between Lake-Cook Road and Dempster Street in Skokie, the railroad was sold to the Chicago & North Western, which became part of Union Pacific Railroad in 1995. The southern section between Skokie and Howard Street became part of the Skokie Swift, a pilot project for mass transit. The railroad featured five miles of length traveled in 6.5 minutes. Since, the route has been re-branded as the CTA Yellow Line. UP abandoned the segment in 2005. From Oakton Street in Skokie to Rockland Road near Waukegan, the grade is used by the Skokie Valley Trail. A gap in the trail currently exists between Skokie and Northfield.
Located north of Howard Street in Skokie, this large viaduct carries the CTA Yellow Line over McCormick Boulevard and an abandoned Chicago & North Western Railway (C&NW) line. Built in 1924-1925 during the construction of the line, the bridge consists of a 120-foot, 8-panel double intersection Warren deck truss main span over the canal (span #8), a 105-foot, riveted, 8-panel Pratt pony truss bridge over the abandoned railroad (span #13). The remainder of the bridge is made up of deck plate girder spans, including two 70-feet spans, one 60-foot span, four 55-foot spans, two 50-foot spans, and one 45-foot and 35-foot spans . The substructures of the bridge consist of steel bents and towers, a concrete pier near the west end of the bridge and concrete "skeleton" abutments. Skeleton abutments were commonly used to control costs and maintenance with the approach embankments. This design allowed the approach embankments to be graded at a flatter slope, helping to minimize erosion. The east abutment of the bridge uses a 45-foot slab span, and the west abutment utilizes a 35-foot slab span. Hansell-Elcock Company was contracted to fabricate the superstructure, and the L.E. Meyer Company was contracted to construct the concrete substructures. The bridge officially opened to traffic in March 1925.
The deck truss span utilizes a typical design for the early 20th Century, with solid members and light riveted connections. The use of a double intersection Warren span is an unusual feature of the bridge. The Niles Center Branch was designed by I.F. Stern, who also was a bridge engineer for the C&NW. The C&NW used lattice and double intersection spans like this extensively, and the railroad swore by the design. It is likely that the design was chosen due to the Engineers relation to the C&NW. The pony truss span utilizes a heavy design, featuring solid members and a floor consisting of plate girders. The pony truss is slightly skewed to account for the angle of the railroad underneath. Since the initial construction, the bridge has seen little change. Overall, the bridge appears to be in fair to good condition, and continues to serve traffic. The author has ranked this bridge as being regionally significant, due to the unique designs and contractors.
Citations
| Build date and builder (superstructure) | The Iron Age; June 12, 1924 |
| Builder (substructure) | Railway Engineering and Maintenance; Volume 22, Issue 8 |
| Railroad History Citation | ICC Valuation Information, Compiled by Richard S. Steele |