In October of 2004, a construction crew working at Coenties Slip in Lower Manhattan hit something four feet down. It was a log—yellow pine, more than thirteen feet long, thirty inches through, with the bark still on it. Running straight down the middle of that log was a hole six inches wide. It had been lying there for two hundred years, put into the ground before 1808 by a company that had promised New York clean water.

Two more came up under Beekman Street in 2006. Philadelphia turned them up in its own streets, most recently in May of 2017. And here is the question almost nobody asks: why would anyone drill a hole through twenty thousand trees and bury them under a city? The answer is one of the strangest and most completely forgotten pieces of engineering in American history, and it starts with a problem that no modern city has.

An American city in 1799 had no way to move water. Not uphill, not across town, not into a house. Water came out of the ground where the ground gave it, and every drop that went anywhere else went there in a bucket, a barrel, or a cart. Philadelphia had public pumps at the street corners.

New York had a single pond and a few hundred private wells, most of them sunk within a few feet of a privy. That worked as long as a city stayed small. Neither of them stayed small. Two things forced the issue in the same decade.

The first was disease. The second was fire, because a bucket line was the entire fire service, and a bucket line could not save a block. It is worth being precise about what that meant day to day. A household in New York either owned a well or bought from a carter, and the carters sold water by the barrel off a horse-drawn cask.

A well in a dense block sat a few feet from a cesspool. Nothing separated the two but the same sandy ground. Brewers, tanners, and dyers all wanted the same water and all fouled it. Public wells were pumped by hand at the street corner, one bucket at a time, and a household that wanted a bath carried the water up the stairs in stages.

So both cities decided to build a water system. Philadelphia started laying pipe in 1801. New York’s company had been chartered two years earlier, in 1799. Now, think about what a pipe actually is.

It is a tube that has to hold pressure, run underground for miles, take a branch every hundred feet, and not fall apart. In 1801 in the United States, there was exactly one material you could get in quantity, in long pieces shaped roughly like a tube already, anywhere near the work. A tree. Cast iron existed.

Cast iron was what the engineers wanted, and they said so. But a cast iron main had to be founded, cast in sections, carted to the trench, and laid by men who had done it before. America had almost none of that in 1800. A log cost what the hauling cost.

A log came out of the woods that the city had just been cleared from. And a log could be made into a pipe by a three-man crew with hand tools in a yard beside the trench. The men who did it did not call it a pipe. They called it a pump log.

Start with the log itself, because the choice was half the job. The straightest stems were taken, because a hole bored through a curved log comes out through the side. Philadelphia used white oak, yellow pine, and spruce. Crews elsewhere wanted cedar or cypress if they could get either, because both resist rot in wet ground, and settled for elm, alder, or oak when they could not.

The bark was often left on, exactly as it came off the stump, which is why the New York pipes still look like trees today. The pieces were cut short. Six feet, eight feet, and twelve feet were the common lengths, and twelve was the longest most crews would attempt. The reason for that is the reason for everything in this story: past about twelve feet, you cannot hold a hole straight.

The log went into a cradle, a low timber frame that gripped it and kept it from turning. One end—the end that would take the next pipe—got an iron band driven around it first. That band was there to stop the wood splitting when the boring started, and it stayed on for the whole working life of the pipe. Then came the boring.

The tool was a pod auger, and the shaft on it ran eight to nine feet long. The cutting end was small, two inches across, and the handle at the other end was a wheel, so that two men could walk it around rather than crank it. There was no jig, no guide tube, nothing to hold the line. The master driller lined the auger up by eye and kept it straight by feel, correcting a drift of a quarter inch over eight feet before it became a drift of two inches over twelve.

And here is the part that is hard to believe when you first hear it. They bored from both ends. A twelve-foot log was bored six feet from one end, then turned and bored six feet from the other, and the two holes had to meet in the middle. Not roughly.

They had to meet cleanly enough that water would run through the joint without catching on a step in the bore. Crews used a wooden gauge with fine adjustments, laid along the outside of the log, to keep the second cut aimed at the first. Everything else was the driller’s hands. When the two bores met, the pilot hole was two inches wide, and the pipe needed to be three, four and a half, six, or, in New York, eight.

So the hole was opened out in stages with reamers. The reamers were heavy bits forged by a blacksmith, each one a step larger than the last. They carried cutting edges on the left and the right side both, so that they cut on a single clockwise turn. Reaming was harder than boring, much harder.

The pilot auger cuts a small circle of wood. A reamer has to peel the whole wall of the hole back along eight or twelve feet against the grain. The standard crew was three men: one master driller and two laborers. On the bigger diameters, the laborers tied ropes to the reamer so that one could pull the blade through the log while the other pushed on the handle.

A single twelve-foot pipe took the three of them a long working part of a day. They checked the meeting point by sight and by water. A pipe was stood on end and a bucket poured in. A bore that ran clean carried the water straight through.

A bore that stepped at the joint held it, and the crew went back in with a reamer until it did not. A log that split during reaming was cut down into shorter service pieces. A log that had been bored crooked came out through the wall and went on the fire. Then, the ends.

The end that would go into the next pipe was hewn down roughly round with a hatchet and finished with a tool called an end shaper, which worked precisely the way a giant pencil sharpener works. A round projection went into the bore to center it, and a blade cut the outside of the log down into a clean taper. The other end, the banded end, was opened out with a reamer into a matching cone. So the joint was a taper driven into a socket.

The male end of one pipe was hammered into the belled end of the next, wood into wood, with the iron band holding the socket together against the wedge. Some crews used a separate wooden collar over the joint instead, strapped with wrought iron. Either way, there was no gasket, no cement, and no thread. The seal was a tapered fit and the swelling of wet wood.

Finally, the whole pipe was coated with pitch or tar to keep ground water out of the grain and dropped in the trench. The trench itself was shallow by modern standards, three to five feet, dug by hand and backfilled by hand. The pipes went in end to end and were driven home with a maul. The blow landed on a block of wood, so that it fell on the whole face of the taper and not on one edge of it.

Then came the part that made it a system rather than a line. A house did not connect to the main. A house connected to a service pipe, and a service pipe was another bored log, smaller, that was cut into the side of the main. A hole was bored through the wall of the buried main.

A smaller tapered pipe was driven into that hole, and the branch ran off toward the building. The line under Coenties Slip in New York fed roughly twenty-five customers that way. When a house stopped paying, the crew dug down to the tap and hammered a wooden plug into it. When a pipe failed, which it did, there was no valve to close.

The crew dug a hole in the street, found the leak, drove a plug, cut out the bad length, and drove a new one in. Philadelphia began laying wooden mains in 1801. By 1832, the city had put 241,604 feet of wooden pipe under its streets. That is forty-five and three-quarter miles.

Those pipes came in three bores: three inches, four and a half inches, and six inches. The six-inch pipe was the main. The four and a half carried a street. The three-inch ran the branches.

All three were the same log with a different tool put through it. Do the division. Two hundred forty-one thousand feet in pieces twelve feet long is roughly twenty thousand logs. Twenty thousand trees cut, cradled, bored from both ends, reamed out in four stages, tapered, banded, tarred, and buried one at a time by crews of three.

That is one city. And Philadelphia was the tidy one. Put a clock on that. Three men, most of a working day, for one twelve-foot length.

Twenty thousand lengths is somewhere around twenty thousand crew days, and none of it is the digging, the hauling, the felling, or the backfill. The pipe alone was years of work by hundreds of men, and not one of them is named in the record. What is in the record is the footage. New York’s system came out of a deal.

In 1799, a state assemblyman named Aaron Burr got a charter for a company to supply the city with water. The charter carried a clause letting the company put its surplus capital into any business it liked. The company used that clause to open a bank, which is the only reason most people have ever heard of it. The waterworks was the part it cared about least.

So it built the cheapest system that could be called a system. Hollowed logs, when the engineers had asked for iron. Yellow pine, bark on, twelve and fourteen feet to the piece with an eight-inch bore on the mains. It worked, after a fashion, for forty years.

Look at what that means on the pipe the crews pulled out of Coenties Slip. Thirty inches across the outside, a six-inch hole down the middle. That is a wall of solid pine roughly a foot thick running the whole length of the pipe. Every inch of that thickness had to be cut away from the bore by hand with a reamer before the log carried a drop of water.

By 1808, the company was serving about two thousand customers, which was under fifteen percent of the households in the city. By 1830, it had forty miles of pipe in the ground and reached maybe a third of New York, and almost none of it ran above Grand Street. Customers complained the water had a color and a taste and that it carried salt. There is one more thing those buried logs did, and it left a word behind that Americans still use.

A wooden main had no hydrants. It had no valves and no risers and nothing at all sticking up out of the street. So when a building caught fire, the fire company did the only thing the system allowed. They dug a pit in the street down to the main, and they bored a hole straight into the top of the pipe.

Water came up and filled the pit. The pit became the reservoir. The pumps drew out of it, and the buckets were filled from it. When the fire was out, a crew drove a wooden plug into the hole, filled the pit back in, and marked the spot so the next company would know where the water was.

The mark said, “There is a plug here. ” That is where the word comes from. Americans still call a hydrant a fire plug. And the plug in question was a piece of wood hammered into a tree.

By 1803, Philadelphia was already building something better: a cast iron riser that ran from the main up to the street. But the name stuck to the thing that replaced it, and it has outlived the pipes by two centuries. Meanwhile, the wood itself was running into its limits, and there were three of them. The first was diameter.

A pipe cannot be wider than the log it came from, minus the wall you have to leave. Eight inches was about the practical ceiling, and eight inches is not much main for a growing city. The second was pressure. A tapered wooden joint holds because it is wedged and swollen, and that is enough for gravity flow from a reservoir.

Push real pressure through it of the kind a fire engine wants at a hydrant, and the joint is the weak point in every single length. The third was rot. Tar and pitch bought years, and cedar bought more years than pine. But a pipe that is soaked at the bottom and dry at the top is a pipe that is being eaten from the inside.

Cast iron fixed all three at once, and by the 1820s, the founding industry finally existed to supply it. Philadelphia started swapping wooden mains for iron around 1820 and worked through the network line by line. In 1858, the city recorded that the last of the old wooden water mains had been taken up and iron pipe substituted. New York did it in one stroke instead.

In 1842, the Croton Aqueduct brought water down from upstate and distributed it through cast iron, and the Manhattan company’s pipes simply stopped being the water supply of New York. Nobody dug them out. There was no reason to. An abandoned wooden pipe in a trench is not a hazard, and it is not worth the labor of lifting.

So the crews cut the lines they had to cut. They laid the new iron beside them and left the rest exactly where it was, which is why they keep coming back. Four feet under Coenties Slip in 2004, under Beekman Street in 2006, under a Philadelphia street in May of 2017, and a dozen times before that in both cities, every time somebody opened a trench in the old grid. And what comes up is always the same thing.

A length of pine or white oak, six or twelve feet of it, bark still on, an iron band rusted into the wood at one end, a taper cut on the other, and a hole running down the middle that three men opened by hand from both ends, working toward each other in the dark until they met.