19 August 2020

Millstone River Bridge and Causeway

Of all the historic bridges in and around Hillsborough, perhaps none have been more important in the commerce and communication of the township than the series of bridges spanning the Millstone River in the village of the same name.

Millstone River Bridge circa 1905

When the first bridge was constructed - probably around 1725 - the Delaware and Raritan Canal was still more than 100 years in the future; the railroads after that. The most direct route to the market town of New Brunswick, and its port, was overland by wagon road. Throughout the 18th century, the farmers of Hillsborough depended on the road and the bridge to get their produce to market.

We don't know exactly what the bridge or bridges that existed in the 1700s looked like, but there are a few things we can say for certain. The bridge would have been wooden, and, the width of the river being too great for a single span, a stone pier would have been required midstream. 

The photo above of the late 19th-century version of the Millstone River Bridge gives a good idea of the configuration of the wooden bridges. We also know those earlier crossings were not in the location of today's bridge but rather just to the north - intersecting with what today is called North River Street.

Millstone River Bridge circa 1906

In 1901 the Somerset County Freeholders commissioned a new bridge at the same location. Originally envisioned as being two spans supported with a stone pier in the middle, the design was changed to a single-span iron bridge.

Millstone River Bridge circa 1908

Although referred to as the "Millstone Causeway", the pedestrian boardwalk was the only element other than the bridge itself that was elevated. The roadway between the river and the Delaware and Raritan Canal was at ground level across the meadows.

Millstone River Bridge and the flooded meadows - looking south, 1905

Flooding of the meadows - which may have only been a nuisance in the 18th and 19th centuries - was considered much more of a serious issue in the 20th. As the area became more developed, properties, especially the commercial and industrial businesses in East Millstone, became very valuable. Constant flooding - not just in Millstone but also in Weston and around Bound Brook - made it impossible for the local fire companies to reach East Millstone during an emergency.

An illustration of the proposed New Millstone Causeway
by Oscar Smith, Jr., County Engineer

It was said that any measurable amount of rain would flood the roadway. This was not such a problem in the days of horses and carriages which could navigate a little water, but in the age of the automobile, it was a disaster. In the 1920s, busses would regularly unload their passengers at one end of the boardwalk and have them walk across to a waiting bus at the other end to continue their commute. But ultimately it was a devastating fire in East Millstone - with fire companies from Manville, Somerville, and Bound Brook unable to reach the town - which led to the consideration of a completely new elevated causeway.

Construction of the New Millstone Causeway circa 1931

The original proposal called for the repaired and strengthened 1901 bridge to remain in place and connect to a new concrete causeway across the meadow. On the East Millstone side, Somerset County officials negotiated with the Pennsylvania Railroad - owners of the canal - over what to do about the canal bridge. These initial plans failed to address the centuries-old problem of the bridge not actually leading to Millstone River Road but rather to North River Street.

14 August 1931 Courier News

A solution was found with the county's acquisition of a small private road called "The Driftway". Never a public thoroughfare, the short street leading from North and South River Street to Millstone River Road became the perfect path for a brand new bridge and causeway. Plans were drawn up in 1929 and preliminary engineering work took about six months. The Courier News gave the statistics for the new bridge and causeway in an August 1931 story heralding the completion of the span:

The bridge is of three spans and is 135 feet long, made of concrete and steel. The causeway starts from the east end of the new bridge and extends for 665 feet, ending in a 300-foot fill connecting the road with the bridge over the Delaware and Raritan Canal in East Millstone. The centers of the 25 spans in the causeway are 27 feet apart. The roadway is 24 feet wide, and approximately 10 feet above the meadow.

A sidewalk, five feet, three inches wide extends along the northerly side of the highway for pedestrians. The piers under the causeway rest on piling, approximately 8,460 lineal feet being used, the piles reaching bedrock 19 feet below the surface. The causeway carries attractive sideway of ornamental concrete and is illuminated with cluster lights at the top of ornamental concrete pillars.

The Millstone Causeway underwent extensive reconstruction in 1998 and continues today as a vital link in Somerset County's 300-year-old transportation network.


  1. I grew up playing under that bridge, massive snapper turtles. Lots of snakes & ducts, unfortunately old tires!! Was there for reconstruction too!! I remember hurricane Adoria (72)
    ABC new borrowed my dads boat!! Bob Lape great memories !!!! Thank you for the great share

  2. I grew up playing under that bridge, massive snapper turtles. Lots of snakes & ducts, unfortunately old tires!! Was there for reconstruction too!! I remember hurricane Adoria (72)
    ABC new borrowed my dads boat!! Bob Lape great memories !!!! Thank you for the great share

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