Main Street Bridge

The Main Street Bridge carries Main Street over the South Branch Raritan River in Clinton, New Jersey, at the point where the river drops over the mill dam between the town’s two surviving mills. Designed by Francis C. Lowthorp and fabricated in 1870 by William and Charles Cowin of Lambertville, it is a pin-connected pony Pratt truss of composite cast and wrought iron, with Italianate end posts and a decorative cast-iron railing along its timber plank sidewalks. ^[1] It is one of three surviving Lowthorp-designed, Cowin-built truss bridges in Hunterdon County, and the longest and only multi-span example among them. ^[3]

The bridge is the fourth or fifth crossing on the site.

A mill stood on the east bank of the South Branch Raritan River as early as 1763, and by 1780 it was being advertised as an oil mill. Daniel Hunt’s name was attached to it in 1778, and Colonel Ralph Hunt’s in 1809, the year a survey for the New Jersey Turnpike was mapped through the valley. ¹

Around 1810, Ralph Hunt built a frame mill on the west bank, on land inherited from his father, and fitted it to process wool. The settlement that grew around the two operations was known simply as Hunt’s Mills. ^{1 4} The venture did not last. The domestic cloth market collapsed after the War of 1812, and by 1820 Hunt was reporting to the census that the establishment had been doing very little for two or three years. He eventually lost more than 400 acres and the mills on both sides of the river. ⁴

The men who picked up the pieces gave the town its name. In the late 1820s John Bray and John B. Taylor took over the Hunt property, added grist and stone plaster to the wool operation, and renamed the village Clinton after DeWitt Clinton, then governor of New York. ⁴ Bray and Taylor were land developers as much as millers. They opened the tavern that became the Clinton House on the west bank around 1825 to 1830, laid out the commercial lots that became Main Street, and sold the ground the Presbyterian congregation built on in 1830. ¹

By the middle of the century the two mills functioned as one industrial complex on opposite banks, offering sawing and plaster along with oil pressing, wool treatment, and wheat grinding. The National Register nomination treats them as one half of the town’s service center. The other half sat across the bridge on West Main Street, where wheelwrights, carriage builders, and a livery clustered opposite the Clinton House. ¹ Everything moving between those two halves crossed the river here.

The east-bank mill burned and was rebuilt in stone in 1836, its date stone reading “C. and J. R. Dunham, rebuilt 1836, J. Housel, mason.” ¹ It is known today as the Dunham/Parry Mill and houses the Hunterdon Art Museum. The west-bank mill went through wool, grist, peach baskets, electricity generation, graphite, and finally talc before closing in 1928. It is now the Red Mill Museum Village. ⁴

The Turnpike

The road across the bridge is older than the bridge and older than the town. Center Street and West Main Street follow an eighteenth-century highway, the Easton-Brunswick Road, which itself traced an earlier Lenape route through the valley. ^{1 5}

In 1806 the state legislature chartered the New Jersey Turnpike Company to improve it as a toll road four rods wide, running from Albany and French Streets in New Brunswick to Easton, Pennsylvania. ² The name is confusing to modern readers, since the modern New Jersey Turnpike has nothing to do with it. Locally the road was called the Easton and New Brunswick turnpike, or simply the Easton Road, and that usage lingered into the twentieth century. ⁵ The turnpike was in place through Clinton by about 1816. ¹

A Ralph Hunt and a John Bray both sat on the turnpike company’s first board of directors, alongside the surveyor and legal records for Hunterdon County landowners in 1809. ² If these are the same men who owned and then bought the mills, and the coincidence of names, dates, and place is difficult to explain otherwise, then Clinton’s founding families were writing the route of the road past their own water power. That connection is worth confirming in the deed record before you state it flatly.

Two other roads shaped the crossing. The Spruce Run Turnpike was chartered around 1813 and would have run north from town along what is now Halstead Street, but it was never fully built. ^{1 5} And Main Street itself was laid out running straight from the river bridge and the mills, at right angles to the turnpike, for two short blocks. The commercial row was oriented to the crossing, not the other way around. ¹

Succession of bridges

Getting across the river and the mill pond has always been part of Clinton’s built environment. A lithograph of 1842 or 1844, reproduced in Barber and Howe’s Historical Collections, shows an early truss form at the site, along with the buttonwood tree that still stands near the bridge and is referred to in a deed of the 1830s. ¹

County records show a version of an iron truss bridge here in 1859, only eleven years before the present structure. ¹ What became of it is not stated in the nomination. Flood damage is the obvious suspect on a river that repeatedly overtopped Main Street, and the town’s response to that flooding is still legible in the streetscape. Every building put up after the Great Fire of 1891 was raised a full flight of steps above the sidewalk. ¹

The Halstead Street crossing upstream ran through the same sequence on a slightly different schedule: a covered wooden bridge first, then an Ithiel Town lattice bridge, then the concrete-encased steel stringer bridge of about 1932 that stands there now. ¹

1870 Bridge

The Board of Chosen Freeholders ordered the replacement in 1870, taking a design by Francis C. Lowthorp and a fabricator in William Cowin of Lambertville. ¹ Cowin’s firm was run with his brother Charles. ³

The trusses follow the Pratt configuration patented in 1844, with the verticals and top chord in compression and the diagonals and bottom chord in tension. What distinguishes the Lowthorp design is the material split. Every compression member is cast iron, shaped rather than rolled, while the tension members are wrought iron. ^{3 6} The result reads as ornamental but is entirely structural. The decoration is the structure.

Because the spans are short, the trusses stand only about nine feet high and were built as pony trusses, without transverse bracing across the top chord. The cartway measures 16.35 feet, flanked by timber plank sidewalks with cast-iron railings. ¹

The bridge names its makers. Raised lettering on each truss records that the Board of Chosen Freeholders ordered the construction, and the fabricator’s name, William Cowin of Lambertville, appears on hexagonal sections. The date is carried in the Italianate end posts. ¹

Alterations have been modest. Vertical members were replaced with rolled steel over the years, the original timber plank deck gave way to an open steel grid on steel stringers, and the original cream paint color has been kept at every repainting. ¹

Recognition

The Main Street Bridge is one of three composite cast and wrought iron Pratt truss bridges built by Cowin that survive in New Jersey. The others are the New Hampton Pony Pratt Truss Bridge of 1868 over the Musconetcong River and the Glen Gardner Pony Pratt Truss Bridge of 1870 over Spruce Run. All three are in Hunterdon County, and they are the only bridges in the state using cast iron for every compression member. ³

It was recorded by the Historic American Engineering Record in 1991 under the name West Main Street Bridge, and added to the National Register of Historic Places on September 28, 1995 as a contributing structure in the Clinton Historic District. ^{1 6}

Inspectors at one point recommended replacing the structure outright. Hunterdon County chose rehabilitation instead, aided by a federal Transportation Enhancement award, on the grounds that it cost less than replacement, required a shorter closure, and left the historic fabric intact.

The trades that once justified the crossing are gone. The wheelwrights and carriage builders on West Main Street were displaced after the Lehigh Valley Railroad ran a spur into Clinton in 1881, and the mills fell silent in the twentieth century. ¹ The bridge outlasted all of it, and still carries traffic between the two mills it was built to connect.