Have you ever been captivated by the elegant curves of a bridge, feeling the weight of history it carries? Today we explore a special chapter in bridge engineering – the concrete bowstring truss bridge, affectionately known as "humpback bridges" in Michigan and Ontario.

Concrete bowstring truss bridges, characterized by their distinctive arched upper chords resembling camel humps, represent an important milestone in early 20th century infrastructure. The design was standardized by C.V. Dewart, Michigan's first professional bridge engineer, with lengths ranging from 50 to 90 feet.

The inaugural structure was completed in 1922 over the Raisin River in Tecumseh, Michigan, marking the beginning of the "humpback" bridge era that would see dozens of similar crossings built across the Great Lakes region.

• Arched Design: The signature humpback appearance results from curved upper chords that efficiently distribute loads to abutments
• Reinforced Concrete: Steel reinforcement provided tensile strength while concrete protected against corrosion
• Standardized Construction: Pre-determined dimensions accelerated production and reduced costs
• Simplified Techniques: On-site casting using wooden forms made construction accessible for the era

Beyond their functional purpose, these bridges became cultural touchstones representing early automotive infrastructure development. Several surviving examples now serve as historic landmarks and tourist attractions.

As of 2012 records, Michigan preserves several notable bowstring truss bridges including:

• US 12–St. Joseph River Bridge (Mottville) - The longest at 270 feet
• 23 Mile Road–Kalamazoo River Bridge
• Lincoln Road–Pine River Bridge
• Vernier Street–Swan Creek Bridge

Maintaining these historic structures requires specialized approaches:

• Regular structural assessments to identify deterioration
• Targeted repairs addressing concrete spalling and rebar corrosion
• Adaptive reuse strategies balancing preservation with functionality

While no longer a mainstream bridge type, bowstring truss designs continue to inform modern engineering through:

• Load distribution principles applied in contemporary arched bridges
• Materials science insights from century-old concrete performance
• Lessons in balancing aesthetics with structural integrity

These bridges stand as physical connections to early 20th century innovation, reminding us of engineering's evolving nature while preserving tangible links to our infrastructure heritage.