New York City's Brick River

In the early 1800s, residents of New York City got their drinking water from sidewalk pumps that tapped into the city’s aquifer. But as industry in the city grew, the water became contaminated with the runoff from breweries, tanneries, slaughterhouses, and waste (both livestock and human).

The city fathers recognized that, if the metropolis were to flourish, it needed a dependable source of clean water. Two seminal events spurred them to action: the cholera epidemic of 1832, during which the water-borne bacteria killed 3,515 residents, and the Great Fire of 1835, which burned for three days and destroyed 17 city blocks in part because of a lack of readily available water.

As a result, in 1837, work began on one of the most ambitious municipal projects of the era: an aqueduct that would bring water from the pristine Croton River 41 miles north of Manhattan into the city. Once there, the water would be stored in two reservoirs, a receiving reservoir in Central Park, and a distributing reservoir on 42nd St. By any account, the aqueduct was an impressive feat of engineering. It was built of bricks and hydraulic cement, the latter being especially resistant to wet environments. It used no mechanical pumps—water flowed to the city by the force of gravity alone. To accomplish that, the aqueduct dropped 13 inches every mile.

To meet that precise requirement, the horseshoe-shaped brick tunnel was secured on a stone foundation and topped by a dirt berm. The berm's telltale round top still marks the path of the aqueduct today.

The aqueduct was far more than a giant brick sluice, however. To prevent a vacuum from forming inside it as water rushed downstream, 33 above-ground ventilators—giant stone “breather” tubes—were built about every mile.

The tunnel sent up to 90 million gallons of water to the city each day, and it needed regular care.

To inspect, maintain, and repair the tunnel, caretakers had to empty the aqueduct. To that end, six stone structures, called weirs, were built along the conduit. They housed giant metal gates that, when closed, shunted the water in the aqueduct to nearby rivers. One of those weirs, in Ossining, NY, is open to the public a few times a year (go here for a tour schedule).

Each weir required a caretaker, who was given the use of a “keeper’s house” near their secton of the aqueduct. Of the six houses built, only the one in Dobbs Ferry, NY, remains in its original location. In 2001, that rundown structure, built in 1857, was fully restored. It now serves as the aqueduct's museum.

Until recently, the Dobb's Ferry building was thought to be the only remaining keeper's house. In 2014, however, a second house, in Ossining, NY, was identified and confirmed. It turns out that in 1928, the house was moved from its location next to the aqueduct to a residential street, where it is now a private home.

Despite the distance the Croton water had to travel, only three bridges had to be built to span obstructions. The most noteworthy was the High Bridge, built in 1848 and modeled after the Roman aqueducts. It stretches 1/4 mile over the Harlem River in northern Manhattan.

The aqueduct cost $13 million to build and took 5 years to complete. Irish immigrants provided most of the labor at the rate of $1 a day.

In 1968, New York State bought 26.2 miles of the aqueduct and opened it to the public as the Old Croton Aqueduct State Historic Park. The flat trail atop the aqueduct is ideal for walking, biking, and cross-country skiing.

The trail winds through commercial areas; residential areas (including people's back yards via easements still in place); the grounds of Lyndhurst, railroad tycoon Jay Gould's riverside mansion; and along the path of many old Hudson River estates.

While modern development means that the aquduct is no longer a contiguous 41 miles, trail maps show workarounds for inaccessible areas.

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