STONE ARCH

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he earliest extant bridge type inDelaware is the stone arch. This wasthe technology that settlers brought to

this country, and it was the technology usedwhen a substantial structure was desiredand the building material was readily avail-able. Four stone arch highway bridges re-main in service on public roads in the state.All appear to date, at least in part, to the19th century with the nucleus of the OldLancaster Pike bridge, southeast of Hockessin,New Castle County (State Bridge NC-617),dating back to the 1808-1811 developmentof the turnpike.

The arch is curved construction with theconvex side upward. It consists of shaped

Lost Delaware Stone Arch Bridges. About 20stone arch highway bridges are known tohave existed in New Castle County in the1920s. Among them were a stone arch bridgesouth of Middletown (left), and a bridge nearThompsons Station and the Pennsylvanialine (right).

blocks called the arch ring that compresstogether under vertical loads. To work, theoutward thrust at the base of the arch mustbe countered by the abutments, and thearch ring must be one compression unit.The technology is well suited for the com-pressive strength inherent in natural rock.Regardless of size or shape, the principlebehind the arch remains the same; the ver-tical forces have to be balanced by equal re-actions at the abutments. The arch shapecan vary from semicircular to elliptical andsegmental.

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BRIDGES Stone arch bridges still in useon Delaware roads date from

about 1810 to 1860.

T

The arch ring supports the spandrel wallsand parapets that hold back the fill placedbetween the arch ring and the roadway. Theparapets in most cases are extensions of thespandrel walls. The arch is constructed bybuilding the abutments and wingwalls andthen erecting a wood, arch-shaped form,known as falsework or centering. The archring stones, spandrel walls, and parapetsare placed, then the structure is backfilledwith fill material (usually stones, largerocks and earth), and the falsework is re-moved, allowing the arch to compress intoa locked and stable unit that supports itselfthrough compression.

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Left: Stone arch bridges were erected by buildingthe abutments and wingwalls and then erectinga wood, arch-shaped form, known as centering,on which the arch ring stones, spandrel walls,and parapets were placed. This drawing from alate-19th-century textbook showed builders oneway of framing the centering.

Stone Arches

Arch Ring

Centering

Abutment

Spandrel Wall

ParapetRoadway

Keystone

SpandrelWall

WingWall

FillMaterial

Intrados

Abutment

Sprin

g Line

Rise

CrownArch Ring

Extrados

Stone Arch Bridges

Two-span stone arch bridge (above right) between Newport andWilmington, New Castle County. No longer standing.

In the early 19th century , turnpike companies built stone arch bridge aspart of their road improvements. Stone arch bridges often eliminated fords,which could be seasonally impassable, or replaced timber bridges. Theyalso conveyed a sense of permanency that turnpike companies needed toattract investors and travelers. Among the turnpike bridges in Delaware

that had survivedinto the 1920swere a stonearch on theLancaster Pikenear Hockessin(bottom left) anda stone arch onthe Concord Pike(top left). Bothbridges are nowreplaced.

Stone arch bridges were usually laid upwith mortared joints, although some weredry laid (no mortar between the stones).Until the late-19th century, the mortarwould have been a soft, plastic, lime-basedmortar rather than a hard Portland or arti-ficial cement. Portland cement came intocommon use in the 1880s and 1890s.

Delaware Department of Transportationphotographic archives for New Castle Countyillustrate that about 20 stone arch bridgesand culverts existed in that county in the1920s. No such records remain for Kentand Sussex counties, but stone arch bridgesare thought to have been uncommon in thelower counties based on the limited avail-ability of native stone. The majority of doc-umented stone arch highway bridges, andall of the surviving examples, are of rubble-coursed fieldstone. The use of fieldstone il-lustrates one great advantage of stone archbridges, the use of a locally abundant nat-ural resource, such as the granite of north-ern New Castle County. Ashlar masonry

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Stone Arch Bridges

was used in Delaware primarily by the rail-roads beginning in the last quarter of the19th century. The state has several largeand impressive railroad stone arch bridgesincluding the 1904 Pennsylvania Railroadviaduct in downtown Wilmington and the1909-1910 B&O (CSXT) bridge over theBrandywine River, north of downtownWilmington at the Augustine Cut-Off.

About the mid 1880s, the general ac-ceptance of metal truss bridge technologyfor highways marked the waning of stonearch highway spans. After the turn of the20th century, however, stone was usedmore often as a decorative, non-structuralveneer on other types of bridges, like rein-forced concrete rigid frames or concrete en-cased multi girders.

The four stone arch highway bridges stillin use on Delaware roads date from about1810 to 1860; three are located in NewCastle County, the fourth in Kent County.The oldest documented example is the Old

Lancaster Pike bridge (NC-617), which al-so holds the distinction as the only surviv-ing stone arch bridge associated withDelaware’s early 19th century turnpike era.

The next oldest stone arch highway bridgeis the approach span to the Rising Sun Lanebridge (NC-1). This 25’-long stone archspan over a former mill race was built in1833 with a Burr arch-truss covered bridgeover the Brandywine River’s main channel.The covered bridge was replaced by a steeltruss bridge in 1928, but the stone arch ap-proach span was retained. Both spans arediscussed in the metal truss bridge chapter.

The other stone arch bridges are the1846 Brackenville Road over Mill Creekbridge (NC-177), southwest of Hockessin,New Castle County, and the circa 1860State Route 6 over Duck Creek bridge (K-39A) between Clayton and Smyrna, KentCounty. They have undergone 20th-centu-ry alterations including widening, but19th-century stone arch elements remain.

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3

4

21

The Locations of Delaware’sHistoric Stone Arch Bridges

1. Old Lancaster Pike over Mill CreekTributaryState Bridge NC-617Hockessin, New Castle County

2. Brackenville Road over Mill CreekState Bridge NC-177Hockessin, New Castle County

3. State Route 5 and Smyrna BranchRailroad over Duck CreekState Bridge K-39CClayton, Kent County

4. Rising Sun Lane overBrandywine CreekState Bridge NC-1Wilmington, New Castle CountyNote: This stone arch span is theapproach span to a metal trussbridge and its individual historytherefore appears in the metaltruss chapter See p. 80).

Old Lancaster Pike (Road 300)over Mill Creek Tributary

State Bridge NC-617Southeast of Hockessin, New Castle CountyDesigner/Builder: Unknown

ca. 1808-1811

The Old Lancaster Pike bridge is Dela-ware’s oldest stone arch highway

bridge and the only surviving bridge asso-ciated with the state’s early 19th century

turnpike era. It is a skewed, 12’-long spancarrying two lanes of traffic on a 26’-widedeck. The bridge has rubble granite span-drel walls and rusticated voussoirs. Theparapets are finished with concrete capsthat replace the original stone capstones.No original plans or drawings are on file atthe Delaware Department of Transportation,but field investigation indicates that thebridge was widened in kind to both sides

Old Lancaster Pike over Mill Creek Tributarybridge. Arch ring detail showing rubble granitespandrel walls and voussoirs, (State BridgeNC-617).

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Stone Arch Bridges

HockessinOld Lancaster

➲

N

41

Lancaster Pike

Bracke

nville R

oad

Pike

Mill C

reekRoad

Mill Creek Tri

buta

ryMill Creek

Old LancasterPike Bridge

NC-617

BrackenvilleRoad Bridge

NC-177

The only known survivingbridge from Delaware’sturnpike era is the ca. 1808-11 Old Lancaster Pike overMill Creek Tributary bridge(State Bridge NC-617).

by approximately 5’, probably near the turnof the century. The nucleus of the stonearch span is believed to date to the con-struction of the 1808 to 1811 Newport-GapTurnpike, later known as the Lancaster Pike.

The Newport-Gap Turnpike was the firstturnpike chartered by the Delaware GeneralAssembly, authorized on January 30, 1808.The route ran from Newport to Gap Tavernin Lancaster County, Pennsylvania, to linkwith the Philadelphia & Lancaster Turnpike,constructed in 1793. The Newport-GapTurnpike provided an important commer-cial link between the farms of LancasterCounty, Pennsylvania and the ports ofWilmington and Newport. Access to theseports and overseas markets stimulated thetrade economy of both areas. This sectionof the turnpike remained the main roadfrom Wilmington to Lancaster until the late1940s, when it was bypassed by a realign-ment of State Route 41.

elaware’s most visually impressivestone arch bridge is the 1909-1910

Brandywine Viaduct built by the Baltimore& Ohio Railroad over Brandywine Creekin Wilmington. The seven-span bridge isslightly less than 1,000’ long and risesover 110’ above the creek. The bridge wasbuilt as the railroad’s replacement of an1888 iron deck truss bridge, which hadproven inadequate to heavier locomotives.Although the B&O could have chosen tobuild another steel truss bridge, or a rein-forced concrete bridge, there were few bridgetypes that spoke to permanency and sta-bility as well as a stone arch, even if stoneconstruction was very costly. The stonearch bridge was built on a slightly down-stream alignment of the older truss bridge.

The Brandywine Viaduct is a testimonyto the economic might and competitive spir-it of America’s railroads during their goldenage. Two rival railroads that competed fordominance of major eastern markets werethe Pennsylvania Railroad and the B&ORailroad. In 1902, the Pennsylvania Rail-road embarked on a major program to re-build its line, replacing many iron bridgeswith trademark stone arch bridges, suchas the viaduct adjacent to its train stationin downtown Wilmington. The rival B&Ofelt obliged to follow suit, and also built

several stone arch bridges.

Historians of the B&O Railroad have oftencriticized its management for expendingcapital on a line that never proved excep-tionally profitable, depleted the B&O trea-sury, and left it financially vulnerable.

The iron truss bridge abandoned by therailroad in 1910 was transferred to the Cityof Wilmington, which converted the bridgefor use by pedestrians and motorized vehi-cles. The state highway department built aroad from the eastern end of the trussbridge to the Concord Pike in 1933. Theroad, which made a more direct connectionbetween the Trolley Square section ofWilmington and the expanding NorthWilmington suburbs, was called theAugustine Cutoff, and the truss bridge hassince been known as the Augustine Cutoffbridge. The deck truss superstructure wasreplaced by DelDOT in 1980. ■

B&O Railroad’sBrandywineViaduct

The B&O Railroad’s Brandywine Viaduct, pho-tographed shortly after it opened in 1910. In thebackground is the 1888 iron truss bridge it bypassed.In the foreground is a pedestrian suspension bridgethat was used by workers walking to and from themills that then lined the Brandywine Creek.

D

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Stone Arch Bridges

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The datestone in the spandrel wall reads “N.C. C. 1846,” indicating the stone arch wasbuilt under the auspices of New CastleCounty’s Levy Court.

BrackenvilleRoad bridge(State BridgeNC-177) is aone-span,26’-long stonearch bridge.

Brackenville Road bridge as it appeared in 1921,before the parapets had been removed and the can-tilevered concrete slab deck added in 1965.

Brackenville Road (Road 274)over Mill Creek

State Bridge NC-177Southwest of Hockessin,New Castle CountyDesigner/Builder: Unknown

1846

Brackenville Road over Mill Creek bridgeis a single-span, 26’-long, stone arch

bridge with rubble fieldstone spandrel walls,arch ring, and voussoirs. The bridge waswidened in 1965 by the addition of a can-tilevered concrete slab deck that resulted inthe removal of the stone parapets. In 1996,the Delaware Department of Transportationreplaced the 1965 deck with another pre-cast concrete slab deck with 3’-wide can-tilevered overhangs and metal beam guiderails. The arch intrados is coated with shot-crete, and the spandrel walls have been re-pointed and patched with concrete. The

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bridge was documented to Historic AmericanEngineer Record standards in 1996. The1846 stone arch bridge, although alteredfrom the deck up, is one of only four stonearch highway bridges identified by the sur-vey. It is historically significant based onthe rarity of traditional stone arch highwaybridges in the state.

State Route 6 and SmyrnaBranch Railroad over Duck Creek

State Bridge K-39CClayton, Kent CountyDesigner/Builder: Unknown

ca. 1860

The skewed, one-span, 18’-long bridgeconsists of a 35’-wide rubble stone

arch on its south (upstream) side to carrytwo lanes of State Route 6 and a 29’-widereinforced concrete arch on its north(downstream) side to carry the abandonedright-of-way of the Smyrna Branch Railroad.The date of construction of the stone archis ca. 1860 based on its style and local his-tory. The date of construction of the rein-forced concrete arch is 1916 based on aninscription in the plain concrete spandrelwall. A concrete sidewalk and a metal beamguide rail were added to the stone arch sideof the bridge ca. 1969. Flared concrete

Route 6 & Smyrna BranchRailroad Bridge

K-36C

➲

N

Smyrna

Clayton

Carter Road

13

300

6

Duck Pond

Duc

kC

reek

Duck C

reek P

arkway

Main St.

Smyrna Branch

Railroad

Stone Arch Bridges

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wingwalls were added to the south side in1984 as part of a project to channelize thestream. Although altered, the bridge is oneof only four remaining stone arch highwaybridges in Delaware and the only identifiedexample of a traditional stone arch highwaybridge south of the canal.

The stone arch bridge was probably builtto provide a permanent crossing of DuckCreek on the road from Smyrna to Claytonafter the latter town was established as astation stop on the Delaware Railroad in1856. The one-mile long Smyrna BranchRailroad was established in 1866 as theSmyrna Station and Smyrna Railroad by lo-cal business interests who desired a betterconnection with the main line. In 1916 thebranch line was regraded and the bridgewidened with the reinforced concrete archaddition by the Delaware Division of thePennsylvania Railroad, which took control ofthe line in 1901. The branch line was aban-doned after 1967. ■

The State Route 6 over Duck Creek bridge is Kent County’s onlyexample of a stone arch highway bridge. It is believed to date to ca.1860 and was probably built to provide Smyrna’s citizens with a per-manent crossing of Duck Creek on the road to the railroad station atClayton. The bridge has undergone numerous alterations, includingwidening with a reinforced concrete arch in 1916 to accommodate arailroad branch line.