With the railroad having gained significant elevation in its climb out of the Naugatuck River Valley, the crossing of Hop Brook involved 300' long and 90' tall trestle, with a 30' tall stone arch structure allowing passage of the brook below. The arch was completed in 1869 and the trestle later filled in during the 1890s. Adjacent to the massive trestle (and later embankment) was a 25' tall by 16.5' wide arch over Church Street, which allowed for one lane of roadway traffic to pass beneath.
In 1937, the New York, New Haven & Hartford abandoned the route over Towantic Hill in favor of a longer, but lower-grade, route via Derby. Three years later, the highway arch was demolished.
Following the devastating 1955 floods, the Hop Brook Dam was one of several flood control structures to be built in the Naugatuck Valley. As part of the dam construction, the railroad embankment was lowered and now carries a dam access road, with Hop Brook still rushing through the nearly 150-year old culvert beneath.