Potomac Aqueduct Bridge

Aqueduct Bridge
First Aqueduct Bridge between 1860 and 1865
Carries	Cargo-carrying boats
Crosses	Potomac River
Locale	Georgetown, Washington, D.C.
Other name(s)	Alexandria Aqueduct
Named for	Aqueduct
Heritage status	Historic American Engineering Record
Followed by	Key Bridge
Characteristics
Material	Wood
Width	110ft
Height	30ft
No. of spans	8
History
Designer	Major William Turnbull
Engineering design by	United States Army Corps of Engineers
Construction start	1833
Construction end	1843
Construction cost	$240,000
Opened	1889
Collapsed	1933
Closed	1923

The Aqueduct Bridge (also called the Alexandria Aqueduct) was a bridge between Georgetown, Washington, D.C., and Rosslyn, Virginia. It was built to transport cargo-carrying boats on the Chesapeake and Ohio Canal in Georgetown across the Potomac River to the Alexandria Canal. The same eight piers supported two different bridges: a wooden canal bridge (a wooden roadway bridge was added on top of the canal later) and an iron truss bridge carrying a roadway and an electric trolley line. The bridge was closed in 1923 after the construction of the nearby Key Bridge. The shuttered Aqueduct Bridge was demolished in 1933.

In 1830, merchants from Alexandria, Virginia, which was still part of the District of Columbia at the time, proposed linking their city to Georgetown to capitalize on the new Chesapeake and Ohio Canal. Congress granted a charter to the Alexandria Canal Company in 1830, and construction soon began on the Aqueduct Bridge that would carry canal boats across the Potomac River and downriver on the south side without unloading in Georgetown. The bridge was designed by Major William Turnbull. Construction of the bridge and Alexandria Canal began in 1833, and both were completed in 1843. To withstand Potomac ice floes, the piers were made of gneiss, with icebreakers made of granite. The water-filled bridge was a weatherproofed-timber, queen-post truss construction. The bridge was 110 feet (33.5 m) wide across the top. It had eight piers, each set on riverbottom bedrock and 7 feet (2.1 m) wide at the top. The third and sixth piers were 16 feet (4.9 m) wide at the top. Each pier was designed so that its top was 30 feet (9.1 m) above the mean high water level. A narrow carriageway ran alongside the bridge. Later, a separate level for pedestrian and carriage traffic was added to the bridge. The tolls from the addition inhibited trade between Georgetown and Virginia, thus benefiting Alexandrian businessmen who retained Virginian trade.