Roebling's Delaware Aqueduct

Roebling's Delaware Aqueduct, also known as the Roebling’s Bridge and the Delaware Aqueduct, is the oldest existing wire suspension bridge in the United States. It is also one of the few suspension bridges in the country that does not follow the typical arrangement of having three suspended spans or one suspended span (this bridge has four suspended spans). In addition, this bridge is unusual because it does not visible towers and cables. The entire suspension system is within the wooden supports for the original aqueduct, which hides the fact that it is a suspension bridge. Note that this timber was removed when the aqueduct was converted to a roadway and was replaced as part of the most recent preservation project, so there are some historical pictures displaying the bridge in a more traditional layout.

The original Delaware and Hudson (D&H) Canal was constructed from 1825 to 1829. It was comprised of 16 miles of gravity railway and 108 miles of canal, containing 108 locks. The canal connected the coal fields of northern Pennsylvania with the markets on the Hudson River.

The D&H Canal expanded throughout the 19th century, with a major enlargement in the 1840’s. This project deepened the canal from five feet to six feet and enlarged the locks to ninety feet by fifteen feet. At the same time, four suspension aqueducts bridges were constructed along the canal to remove the rope ferries. These four aqueduct bridges were the Lackawaxen Aqueduct (which no longer exists), the Neversink Aqueduct (remnants are preserved in the Neversink Valley Area Museum in Cuddebackville, NY), the High Falls Aqueduct (remnants are visible near the D&H Canal Historical Society and Museum in High Falls, NY), and the Delaware Aqueduct, which is still standing and is in use.

The Delaware Aqueduct was constructed from 1847 to 1849 and carries the D&H Canal over the Delaware River. This location had always been a bottleneck along the canal, as the canal boats would have to use a rope ferry to cross the river at the same time as timber was being floated down the river to shipyards and industries in Trenton and Philadelphia. There were frequent collisions between the canal boats and timber rafts, which often led to fighting. The construction of the Lackawaxen Aqueduct and Delaware Aqueduct reduced canal travel time by one full day.

The Delaware Aqueduct operated until the canal closed in 1898. At this time, the aqueduct was drained, and was converted to a private toll bridge for wagons, and later for vehicles. The canal sides and towpaths were eventually removed. The protective ice breakers were not maintained and were eventually destroyed by the river. A tollhouse was built around 1900 and the bridge continued to function as a toll bridge until 1979.

The bridge was purchased by the National Park Service in 1980 with the intent of preserving it as part of Upper Delaware Scenic and Recreational River. In 1986 the NPS rebuilt the bridge’s superstructure from Roebling’s original plans and specifications. The bridge underwent another rehabilitation project in 1995, and the wooden icebreakers, towpaths and aqueduct walls were all reconstructed. This restored the bridges original appearance as an aqueduct, although it still carries a roadway and is not filled with water.

Almost all the ironwork are the same materials that were installed when the structure was originally built, including the cables, saddles, and suspenders. The two suspension cables are made of wrought iron strands and were spun on site in 1847. These strands are held in place by wrapping wires, which were replaced in 1985. The wooden superstructure was replaced about every 25 years by the D&H Canal Company, with the last original timbers being removed in the 1930’s.

No description of the Delaware Aqueduct would be complete without mentioning the engineer, John A. Roebling. Roebling was a German American engineer, who moved to the USA in 1831. He began engineering again in 1837 by building canals and conducting surveys across Pennsylvania. In 1844 he constructed the Allegheny Aqueduct, and in 1845 he built a suspension bridge over the Monongahela River at Pittsburgh. In 1848, Roebling began the construction four suspension aqueduct bridges, including the Delaware Aqueduct. This is the earliest surviving work of John A. Roebling. Roebling went on to design and construct many more bridges, and was eventually joined by his son, Washington Roebling. Among other bridges, they designed and constructed the Cincinnati-Covington Bridge (now called the John A. Roebling Suspension Bridge) and the Brooklyn Bridge.