Supplement to 26

Formal planning of the Capital Beltway began in 1950 and it was included as part of the Federal Aid Highway Act in 1956 ( image #12 ) even before construction actually commenced in 1957. Although initially known as the Washington Circumferential Highway in planning stages, a number of names were proposed for the highway including Colonial Beltway, Colonial Parkway, Capitol Beltway, and Capital Ring before the designation Capital Beltway was retained in June 1960. The Maryland side of the Beltway was primarily designed by the engineering firm, Michael Baker Corporation.

Built in the winter of 1963, the Capital Beltway Bridge over Cabin John Creek was one of the final sections of road to be constructed prior to the opening of the Maryland side ( I-495 ) in August 1964. The northbound and southbound sides of the bridge are actually separate structures, each of a length of 253 feet, running parallel to each other with only a few inches of space between. The bridge initially comprised a six lane beltway ( three per side ) but was widened, in 1970, to accommodate eight lanes of traffic ( four per side ) in an ongoing effort to expand the capacity of the beltway. The total width of the eight lane bridge is approximately 72 feet.

The bridge has an average daily traffic of 38,000.

Bureau of Public Roads. "Washington and adjacent areas". General Location of National System of Interstate Highways Including All Additional Routes at Urban Areas Designated in September 1955. Cartography by BPR.


Supplement to 25

Image #25 provides a second view of the Baltimore & Ohio Railroad bridge over the Big Monocacy River. In image #1, the view shown is from between two parallel deck plate girders, upon which the railroad tracks rest. The current photograph shows the interior structure of the deck plate girder systems, two steel I-beams bolted together to form a web. Three of the six stone bridge piers, including that visible in the foreground, were built in the late nineteenth century for a bridge that has since been replaced.

The photograph looks across the river to the west.

Blueprint from Baltimore & Ohio railroad engineering field notes of ICC parties surveying the physical property of railroads, 1914-29. Courtesy of the National Archives, College Park, MD


Supplement to 24

Image #24 shows the reflection of the Brunswick Bridge. Constructed between 1953 and 1955, the bridge crosses the Potomac River at the location of of Brunswick, MD This city, first laid out in 1780, changed names twice in the nineteenth century. Initially named Berlin by the landowner Leonard Smith, it was renamed Barry in 1832 by the U.S. Postal Service to avoid confusion with another Berlin located in Eastern Maryland. The name was changed to Brunswick by the Baltimore & Ohio Railroad in 1890 to reflect the large number of railroad workers, originally from Brunswick, Germany, who had settled in the city.

With a total length of 2,430 feet, the Brunswick Bridge was constructed as a steel girder and concrete floor beam system linking 18 piers across the river. It is the third bridge constructed across the Potomac in that location. The first was a wood-covered bridge built by the Loudoun and Berlin Bridge Company in circa 1857. It was destroyed by the Confederate army in June 1861, suffering a fate similar to that of the bridge at Point of Rocks ( image #23 ). In 1893 the bridge was rebuilt as an iron through truss bridge on the stone foundations of the previous bridge. This structure was removed after 1953, when a modern bridge was constructed on new piers slightly upstream, as can be seen at the top of the first site plan below.

State of Maryland State Roads Commission, Proposed Bridge over the Potomac River at Brunswick, MD, Plan and Profile, C & O Canal Files, National Capital Parks, National Park Service, Record Group 79. Courtesy of the National Archives, College Park, MD


Supplement to 23

Completed in circa 1939, the Potomac River Bridge connects the US 15 roadway between Point of Rocks, MD with Leesburg, VA. The plans for the bridge were drawn using a rare camelback through truss design in the months following a great flood of March 19, 1936 that had devastated the town of Points of Rocks.

As seen on the first site plan, below, the piers of the current bridge (spaced 165 feet apart) were constructed on the ruined foundations of a previous bridge. The latter was once a 1360 foot long double-track rail bridge connecting the Baltimore & Ohio Railroad to iron ore mines on the Virginia side of the Potomac. It was built in circa 1850, for approximately $60,000, by the Potomac Iron Company which transported its products on both the Baltimore & Ohio Railroad and Chesapeake & Ohio Canal. In 1861, the original bridge was mined and destroyed by the Confederate army led by Captain Turner Ashby.

State of Maryland State Roads Commission, Plans of Bridge over the Potomac River at Point of Rocks, C & O Canal Files, National Capital Parks, National Park Service, Record Group 79. Courtesy of the National Archives, College Park, MD


Supplement to 22

Little Monocacy Creek Culvert is located along the Chesapeake & Ohio Canal half a mile upstream from Lock 27. The culvert has had a tumultuous history. Built circa 1831, the inflow side of the culvert (called the berm side; depicted in the photograph), was repeatedly damaged or destroyed by natural and manmade disasters.

The culvert was first severely damaged in a flood in September 1843 when high water caused the east berm corner to settle, resulting in the collapse of the upper walls. That same year, a new foundation and abutment walls were constructed to repair the damage. In September 1862, during the Civil War, Major General D. H. Hill led a division of Confederate troops that wrecked the structural integrity of the culvert in order to breach its roof and drain the canal. The Union army patched the breaches in the culvert by mid-October of the same year. However, the repair work was hastily done and by 1872, W.R. Hutton, Chief Engineer of the Chesapeake & Ohio Canal Company, reported the that berm side of the Culvert was again cracked and in need of repair. In the early twentieth century with the abandonment of the canal, the culvert was no longer maintained, leading to the complete collapse of 8 to 16 feet of the barrel of the culvert on the berm side (seen in the photograph below) and endangering the structural integrity of the canal.

In 1976, the culvert was finally fully repaired and stabilized with modern cast concrete.

Blueprint of Little Monocacy Creek Culvert, mile post 41.97 (left), C & O Canal Files, National Capital Parks, National Park Service, Record Group 79. Courtesy of the National Archives, College Park, MD. Photograph of Damage to Berm Side (right), photographer Thomas Hahn. From the Thomas Hahn Chesapeake and Ohio Canal collection, circa 1939-1993, at George Washington University.
Special thanks to Yuriko for helping to photograph Image #22.


Supplement to 21

Image #21 shows the interior of the Stone Cutting & Dressing Building at Seneca Quarry. (The exterior of this same structure is visible in image #8). While the quarry was active from the late eighteenth century to its closure in 1901, the cutting building was constructed in circa 1837. The walls of the building, made of Seneca red sandstone, have survived; however no trace remains of the original timber roof.

Water purchased from the adjacent Chesapeake & Ohio Canal ran through an external water wheel (replaced later with a more efficient turbine) and rotated a large drive shaft running through the center of the building within a stone-lined 5 by 6 foot machinery trough, indicated in the blueprint below. Power generated by the shaft was transferred to the cutting and polishing machines via a system of belts connected to pulleys overhead. The cutting and polishing machines took one hour to make a cut one inch deep in a block of red sandstone one foot thick.

The photograph was taken from within the trough, looking towards the southeast interior wall of the Stone Cutting & Dressing Building.

Blueprint and photograph, circa 1953, of the Seneca Quarry Stone Cutting Building, Seneca, MD from the Division of Mechanical and Civil Engineering, Museum of History and Technology under the direction of the National Park Service, 1972.


Supplement to 20

Image #20 looks across the Seneca Aqueduct (also known as Aqueduct No. 1) from within the drained channel of the Chesapeake & Ohio Canal. The water of Seneca Creek is visible in the foreground with the unused channel extending towards the background. Built by the contractors Holdsworth and Isherwood for a total cost of $24,340.25, the aqueduct was the first of eleven intended for the canal. It was built between October 1828 and April 1832 of red sandstone mined from the neighboring Seneca Quarry (image #8). Three identical 34-foot arches supported the aqueduct over Seneca Creek. At the downstream end, it connects directly to Lock 24. 

The blueprints below show the initial design as well plans for the repair of the aqueduct following the collapse of an arch in flooding on September 12, 1971. In 1980 the aqueduct was stabilized with steel beams and pipes but the destroyed arch has not been rebuilt.

Seneca Aqueduct (left), Measured and drawn by Guttersen & McGrew, July 6-12, 1939. Seneca Aqueduct Repair (center & right), Designed and drawn by T.E. Fields, March 21, ’80. C & O Canal Files, National Capital Parks, National Park Service, Record Group 79. Courtesy of the National Archives, College Park, MD.

Special thanks to Mark for help photographing image #20.


Supplement to 19

Lock 12 is constructed of dark granite sourced from a quarry near Glen Echo, MD, with coping of dark red sandstone. It is constructed of similar materials to those used in Lock 13 (image #5). Although the two locks are less than 0.1 miles apart, their designs are significantly different.

Based on a plan from 1828, Lock 12 was intended to be filled with water through three culvert openings within each lock wall. Debris often clogged the openings of the culverts in this design and, in circa 1870, a bypass flume was added to resolve this issue. Originally, swing gates were used on the upper and lower ends of Lock 12. In the 1870s, in order to reduce travel times of the boats passing through, a drop gate was installed in the upper end. This was a solid partition across the lock that was raised and lowered by operating a metal wheel gearing system, a variation on the swing gates that open in the center (of which an example can be seen in the photograph of Swain’s Lock, image #7). 

The construction of a drop gate necessitated the rebuilding of the upper end of the lock and added 10 feet to the internal length of the lock, from 91 feet to 101 feet. In comparison to the original stone work, the rebuilding of the upper lock walls was poorly done: today, these walls regularly leak water.

Drop Gate Details at Lock No 12, Measured and Drawn by Guttersen, April 28, ’33. C & O Canal Files, National Capital Parks, National Park Service, Record Group 79. Courtesy of the National Archives, College Park, MD.