Fox River Aqueduct - Ottawa, Illinois - Ancient Aqueducts on Waymarking.com

"The massive Fox River Aqueduct stands as perhaps the single greatest engineering feat on the I & M Canal.  The construction of the 464-foot long aqueduct was entrusted to a remarkable family, the Sangers.  Family patriarch David Sanger helped build the Erie Canal, and his son Lorenzo built Lock 15 and the Joliet Penitentiary. Work on the aqueduct began in 1838 and eventually cost over $100,000 ($2 million dollars in today's money), making this one of the most expensive sections of the canal.

The steel trough that carried the canal was originally built in wood and after suffering years of damage from ice jams, the original limestone piers were recently repaired.  Today the aqueduct provides a sense of the engineering challenges of canal building.  To keep water and boats moving 96 miles between Chicago and LaSalle, the canal required culverts and dams, five aqueducts, 17 locks, a pumping station and four feeder canals.  While the aqueduct no longer carries water, the I & M Canal State Trail traverses it, giving hikers and cyclists an impressive view." ~ text of information sign