Patterson Viaduct

Patterson Viaduct
Patterson Viaduct Ruins, 1970
Official name	Patterson Viaduct
Crosses	Patapsco River (before 1868)
Locale	Ilchester, Maryland
Design	Arch bridge
Total length	360 feet (110 m)
Longest span	55 feet (17 m)
Clearance below	43 feet (13 m)
Opened	December 1829
Closed	1868
Coordinates	39.248889°N 76.764722°W / 39.248889; -76.764722

The Patterson Viaduct was built by the Baltimore and Ohio Railroad (B&O) as part of its Old Main Line during May to December 1829. The viaduct spanned the Patapsco River at Ilchester, Maryland. It was heavily damaged by a flood in 1866 and subsequently replaced with other structures.

History and design

The viaduct was constructed during the first building phase of the railroad, which extended from Baltimore, Maryland to Ellicott's Mills. The Patterson, the third bridge built for the B&O, was similar in construction to the company's first bridge, the nearby Carrollton Viaduct. It was designed by Caspar Wever and built under the supervision of John McCartney, one of Wever's assistants. McCartney received the contract to build the Thomas Viaduct as a result of his successful completion of the Patterson contract.

The bridge was constructed of granite blocks and was approximately 360 feet (110 m) in length, rising about 43 feet (13 m) above its foundations. It had four graduated arches — two of 55 feet chord (17 m) each and two of 20 feet (6 m) chord each. The smaller arches were introduced for the accommodation of two county roadways, one on each side of the river. The exterior surfaces of the granite blocks were undressed, or rusticated.

Ilchester Tunnel

The viaduct was almost totally destroyed in an 1866 flood. A single-span Bollman Truss built into the west abutment in 1869 incorporated the original roadway arch and upstream wing wall. The Bollman design was supplanted by another bridge before the railroad was realigned about 400 feet (120 m) upstream in 1902–1903 with the opening of the Illchester Tunnel.

Today, all that remains at the original crossing is the single masonry roadway arch of the 1829 construction on the west bank and the stone abutment on the east bank, just south of the present railroad bridge. In 2006 a cable-stayed footbridge, with a design that echoes a Bollman Bridge, was added atop the abutments.

The Patterson Viaduct Ruins were listed on the National Register of Historic Places on June 3, 1976.

References

• Maryland Historical Trust, Crownsville, MD. "Patterson Viaduct Ruins." Accessed 2012-01-12.