In the year 1824, Benjamin Wright, a chief engineer who had already earned the title father of American civil engineering on the Erie Canal, set about 2,600 men to work digging a canal across the narrow neck of land where Maryland meets Delaware. Over the next five years, those men would carve a trench three miles long straight down through a ridge of high ground, moving the earth entirely by hand. And they would fight an enemy no engineering drawing had ever prepared them for. More than 375,000 cubic yards of earth slid down off the walls of that trench and fell back into the channel the men had just dug out.

The place is called the Deep Cut of the Chesapeake and Delaware Canal, and it remains one of the hardest things ever carved by human hands on the American continent. The idea behind the canal was far older than the men who dug it. The Delmarva Peninsula is a long arm of land hanging between two great bodies of water: the Chesapeake Bay on its western side and the Delaware River and Bay on its eastern side. A ship wanting to pass from one to the other had no short way across because the peninsula stood like a wall of earth.

The dream was to cut a channel through the narrow neck at the head of that peninsula, turning a voyage of many hundreds of miles into a passage a vessel could make in a single day. The Chesapeake and Delaware Canal Company was chartered in 1802, making it one of the very first canal projects in the young United States, sometimes called the parent of American canals. But a charter is only ink on paper. Between the signing of that charter and the first true digging lay more than twenty years of surveys, arguments over money and routes, and plans begun and abandoned.

It was not until 1824 that the shovels finally bit into the ground for good. The canal’s value lay in what it saved. Without it, a merchant vessel carrying flour, coal, lumber, iron, or grain between the Chesapeake and the Delaware had to sail the whole length of the Chesapeake Bay, out into the open Atlantic, around the southern end of the entire peninsula, past Cape Charles, and up the coast toward Cape Henlopen before entering Delaware Bay. That detour stretched several hundred miles and was open to Atlantic storms and hidden shoals.

For merchants in Philadelphia on the Delaware and Baltimore on the Chesapeake, a channel of about fourteen miles across the neck of the peninsula was worth almost any price. In the early 1800s, the dawn of the canal age in America, the surest way to move heavy freight was by water. A single boat on a canal could carry many tons behind one team walking the towpath, while loaded wagons on rutted dirt roads broke down men and horses alike. To cut a canal through a ridge was as bold and costly as anything the young country could attempt.

Benjamin Wright had learned his engineering the hard way, out on the real ground of the Erie Canal, where he had served as chief engineer of the greatest public work of the age. He brought that hard-won knowledge down to the Delmarva Peninsula. Working beside him was John Randel Jr. , the surveyor and engineer who had laid out the great street grid of Manhattan.

Randel was brilliant, exact, and famously hard to work with, but his skill was real, and his hand is in the surveying of this passage. On this project, his path with the company would end in bitter dispute, as such things often did with Randel. Now came the central problem. Running across the neck of the peninsula was a spine of high ground, a stubborn ridge.

A canal cannot climb a hill. The engineers had two choices: build a ladder of locks to lift boats over the high ground, which demanded an endless supply of water at the top, or cut down through the ridge until the floor of the channel was low enough for water to lie flat and quiet across the gap. They chose to fight the ridge head-on. Their plan called for a summit level, a stretch of canal held at one steady height across the high middle of the route, guarded by locks at either end.

To hold that summit level, they had to remove the whole crown of high ground that rose above the waterline. They had to dig a canyon through it. That canyon is the Deep Cut. Of the roughly fourteen miles of finished canal, about three miles ran through this one section, and those three miles would swallow more labor, money, and suffering than all the rest combined.

There were no machines. No steam shovels, no excavators. At the height of the work, about 2,600 men labored along the line, and they were not one single people. There were Irish immigrants who had crossed the ocean because such work was what the newly arrived and the poor were given, and laboring alongside them were African-American men whose sweat went into the channel just as surely.

Both groups built this canal. For wages of about seventy-five cents a day, these men worked the raw ground with picks, shovels, hand barrows, and horse-drawn carts. They broke stone, loaded earth, and hauled the spoil up out of the trench. This was Maryland and Delaware in the 1820s, and these were slave states.

The surviving records speak of Irish laborers together with African-American laborers, but they do not tell us cleanly whether those African-American men were free or enslaved. What can be said plainly is that African-American hands and Irish hands carved this passage side by side for pennies a day in heat and cold and mud. The Deep Cut was not driven through clean rock that a man could split and stack. It was driven through a treacherous mixture of boulders, gravel, sand, clay, and water, all layered and churned together with no order a man could count on.

In one stretch a laborer might sink his pick into heavy blue clay that clung to the iron like glue. In the next, he might strike a buried boulder that had to be broken apart or dragged out by chains and horses. And everywhere there was water, seeping up from the floor and sides, turning the ground soft and treacherous. As the men dug downward, the cut grew into a true canyon.

The walls could not stand straight up; they had to be sloped back at an angle so that, in theory, they would hold their own weight. On paper, those regulated slopes were figured to stand. In the real, wet, unstable ground of the ridge, they would not stand. More than 375,000 cubic yards of earth slid down from those slopes and fell back into the channel the men had already dug clear.

The men would dig a length clean, and then the saturated ground above them would let go and come down in a slow, heavy avalanche of mud and gravel, filling the trench they had just emptied by hand. Then they picked up their shovels and did it again. Every one of those 375,000 cubic yards that slid back in had to be dug out a second time by the same hands for the same seventy-five cents a day. There was mortal danger in it as well, for when a wall of water-soaked earth lets go above men at the bottom of a deep cut, there is little warning and little time to climb clear.

That same enemy would humble the builders of the Panama Canal decades later at the Culebra Cut, where whole hillsides of soaked earth slid down into the channel again and again. The men of the Chesapeake and Delaware Canal met that foe first, back in the 1820s, with far less machinery and knowledge. The Deep Cut devoured money as fast as it devoured labor. Earth dug two and three times over must be paid for two and three times over, and the cost ran far beyond what anyone had reckoned.

More than once the company was pushed to the edge of ruin, and only stubbornness and fresh infusions of money carried the project through. High above that terrible notch in the earth stood the Summit Bridge. When the men cut the canal down through the ridge, they opened an enormous gap where a road had once run level across the high ground. The builders threw a great covered wooden bridge across the void, spanning about 250 feet between its abutments, carrying the road high over the canal far below.

It let the wagons and walkers of the countryside go on crossing over the very wound the diggers had opened. After five years of labor, the canal at last was opened. In 1829, water filled the channel from the Chesapeake to the Delaware, and vessels began to slip through the neck of the peninsula that had blocked their way for as long as anyone could recall. The original canal ran about fourteen miles and used locks to lift and lower boats, holding that guarded summit level across the high ground through the Deep Cut.

Boats were worked along it slowly and carefully, and every passage paid a toll to the company. It was a toll road of water, a private enterprise built to earn back the fortune it had cost. A summit-level canal is a thirsty thing. Every time a vessel passed through a lock, a great gulp of water spilled away, and the summit had to be fed from some source or it would run low and the passage would fail.

At first the engineers made do with natural flow from the land around, but it was never quite enough. In 1837, a steam pump was installed to raise water into the canal from a nearby creek. In 1852, that pump was replaced by a steam engine turning a great water wheel that scooped water up and lifted it into the canal above. These machines came after the digging was done, the answer to a burden the diggers had left behind.

For all its troubles, the canal did the very thing it was built to do. It knitted together the trade of two great American ports. Ships no longer had to make the long and dangerous run around the whole peninsula. Coal and grain, lumber and iron, flour and merchandise of every kind moved between the Chesapeake and the Delaware through the channel the laborers had cut.

Philadelphia and Baltimore were drawn closer together than geography had ever before allowed. Even as the restless ground of the Deep Cut kept the engineers forever busy holding its slopes in place. Most of the great hand-dug canals of that age are gone now, killed by the railroads. The Chesapeake and Delaware Canal could very easily have died that same quiet death, but it did not.

In 1919, the federal government bought the canal for about two and a half million dollars and placed it in the hands of the United States Army Corps of Engineers. The government understood that a passage across that neck was far too valuable to let crumble away. It should no longer be a private toll ditch forever fighting its own locks and landslides. It should become a public highway of water.

The Corps resolved to remove the old locks altogether and turn the whole waterway into a sea-level channel, so that ships could pass straight through without being raised or lowered. By 1927, that great work was done. The locks were gone, the summit level was cut away entirely, and in its place ran an open level channel from bay to bay. The Corps then widened and deepened the canal again in the 1930s and again in the 1970s to carry the ever-larger vessels of a new age.

Every one of those enlargements followed the same line across the peninsula, the same passage first opened by hand a century before. The modern channel is wider and deeper, but it runs where the Deep Cut runs, through the same ridge, past the same place called Summit. Today the Chesapeake and Delaware Canal is a fully modern, sea-level commercial ship canal run by the Army Corps of Engineers. It is a vital link in the Atlantic Intracoastal Waterway and serves as the main maritime gateway to the port of Baltimore.

It carries on the order of 15,000 vessel transits in a single year, placing it among the busiest ship canals in the nation and in all the world. Ocean-going cargo ships, tankers, and towering container vessels pass along it steadily by day and night. The canal those ships travel today is not plank for plank the same canal the laborers finished in 1829. It has been rebuilt, widened, deepened, stripped of its locks, and lowered to the level of the sea.

But the passage itself, the line, the very neck of land, is the one they opened. Few of the drivers on the high bridges overhead and few of the crews on the ships below give a thought to the 1820s, to the picks and barrows, to the 2,600 men and the seventy-five cents a day. The canal simply works, hour after hour and year after year, carrying the trade of a nation through a wound in the earth that has long since healed over into a highway. So many of the great hand-dug works of that era are dead and gone, but this one lives.

When you stand on a high bridge and watch a loaded ocean freighter slide quietly through the notch in the land, you are watching traffic move through a channel whose course was first cut by hand through boulders and clay and ground as treacherous as quicksand, by about 2,600 Irish and African-American laborers fighting 375,000 cubic yards of sliding earth in the Deep Cut. Their locks are gone and their summit is gone, but the passage they opened is still in daily use, one of the busiest in the nation.