How lighthouses were built in the 1800s and in the open ocean: Eddystone, Bell Rock, Minot's Ledge, the screw-pile, the caisson, the Fresnel lens and the keepers

Architecture · 4 September 2026

A lighthouse of the 19th century was built in one of four ways depending on where it stood: on land, as a tower of brick or stone with a spiral stair and a lantern, the way Cape Hatteras (1870) and most American lights were built; on a rock in the sea, as a tower of interlocking granite laid in the hours between tides, the way John Smeaton built the Eddystone in 1759 and Robert Stevenson the Bell Rock in 1810 and the Americans Minot's Ledge in 1860; on soft bottom in shallow water, on iron screw-piles turned into the sand, the way the Chesapeake and Florida lights were built from 1850; and in deep water, on an iron or concrete caisson sunk into the sea bed, the way the harbour lights of New York and the Delaware were built from 1870. All of them carried, from the 1850s, the Fresnel lens, a beehive of glass prisms that made an oil lamp visible 20 miles, and a keeper who trimmed it. Below: the ancestors, the rock towers and how they were laid, the American towers, the piles and caissons, the lens and the light, the keepers, the numbers, and the myths, with the 132 lights of the American lighthouses collection, from Sandy Hook of 1764 to Split Rock, as the examples.

Before the 1800s

The Pharos of Alexandria, built by Sostratus of Cnidus about 280 BC, was a tower of about 100 m in three stages, with a fire at the top reflected by a mirror, that stood for 1,500 years until earthquakes brought it down and gave every language its word for lighthouse; the Romans built towers at Ostia, Dover and La Coruña, whose Tower of Hercules of the 2nd century is the oldest lighthouse still working. The lights of the Middle Ages and after were coal fires in iron baskets on towers, the "chauffers", and candles behind glass; the first American light was Boston Light of 1716 on Little Brewster Island, rebuilt in 1783 after the British blew it up, and Sandy Hook of 1764 in New Jersey, an octagonal tower of rubble stone 26 m high, is the oldest still standing and still lit. The technology of the 1800s changed everything twice: the open-sea tower of interlocking stone from 1759, and the Fresnel lens from 1823. Lighthouse.

The rock towers: Eddystone and Bell Rock

• Eddystone, England, 1759. The Eddystone rocks, 14 miles off Plymouth, had wrecked ships for centuries; Winstanley's timber tower of 1698 was swept away in the storm of 1703 with him in it, Rudyerd's of 1709 burned in 1755, and John Smeaton, a civil engineer, built the third in 1756–59 of granite and Portland stone, on a new principle: the tower curved like the trunk of an oak, wide at the base, and every stone was cut with dovetails to lock into its neighbours and with marble dowels into the course below, set in a hydraulic lime he had worked out for the purpose, so that the tower was one piece the sea could not pull apart; he built it in the hours of low water over three summers, and it stood until 1877, when the rock under it was found to be undermined, and it was taken down and re-erected on Plymouth Hoe. Every rock lighthouse since is Smeaton's.
• Bell Rock, Scotland, 1810. A reef 11 miles off Arbroath that is under water except for two hours at low tide, twice a day; Robert Stevenson, the founder of the family that built Scotland's lights for four generations and Robert Louis Stevenson's grandfather, built a tower of 36 m on it in 1807–10, with 60 men living on a ship anchored beside the reef and then in a timber barrack on legs over the rock, landing at each low tide to cut the foundation into the rock with picks and then lay the granite courses, 2,835 dovetailed blocks cut on shore at Arbroath to fit, in the two hours before the sea came back; three summers, no deaths on the rock, and the tower has not been touched since. It is the oldest sea-washed lighthouse in the world still working.
• Skerryvore (1844), Wolf Rock (1869), Fastnet (1904), Bishop Rock (1858, 1887). The Stevensons and the Douglasses built the rest, Skerryvore the tallest at 48 m; the Fastnet, 8 miles off Ireland, took 2,074 granite blocks of up to 3 tons in five years, and the first tower on the site, of iron, was abandoned when a storm bent it.

Minot's Ledge and the American rock towers

Minot's Ledge, off Cohasset, Massachusetts, is a rock exposed only at low water, where forty ships had wrecked; the first lighthouse there, an iron skeleton on nine piles screwed into the rock, built in 1850 on the theory that the sea would pass through it, was carried away in the storm of April 1851 with its two keepers, who rang the bell until the end. The Army engineer Joseph Totten then designed a Smeaton tower of granite, and Barton Alexander built it in 1855–60: the rock was cut level in the few hours a year it was dry enough, the 1,079 blocks of Quincy granite were cut and fitted on shore, each dovetailed to five neighbours and dowelled to the course below, and laid in the summers, 130 working days in five years, with the men living in the schooner; the tower is 35 m, solid for its first 12 m, and was called the most difficult construction in the history of American lighthouses, at 300,000 dollars, the most expensive. Its light, one-four-three, is the "I love you" light of the New England shore. St George Reef in California (1892), on a rock 6 miles out, took ten years and 700,000 dollars and was the most expensive of all; Tillamook Rock in Oregon (1881), "Terrible Tilly", was built on a rock whose top had to be blasted off, with the sea throwing rocks through the lantern.

The land towers: brick on sand

• Cape Hatteras, North Carolina, 1870. The tallest brick lighthouse in America and in the world, 64 m, of 1.25 million bricks on a foundation of timber and granite floating on the sand, built in 1868–70 to replace a shorter tower, with its black-and-white spiral painted for a daymark; the Atlantic ate the beach until the tower was 40 m from the surf, and in 1999 the whole tower, 4,800 tons, was jacked onto rails and moved 880 m inland in 23 days, the largest such move ever.
• Brick towers. The standard American light after 1850: a conical or octagonal tower of brick, double-walled with an air space, on a foundation of stone or piles, with a cast-iron spiral stair, a watch room and the iron lantern on top; St Augustine (1874), Pensacola (1859), Bodie Island, Currituck, the Great Lakes towers of Michigan; the Lighthouse Board bought designs and repeated them, and the towers were painted in patterns so that a captain could tell them apart by day.
• Cast iron. From the 1840s, towers of bolted cast-iron plates lined with brick, made in a foundry and shipped in pieces, for the South and the Great Lakes, and the "skeleton" towers of iron frame for sandy coasts; Cape Canaveral's of 1868 is cast iron and was moved in 1893.
• Range and height. The light had to be high enough to be seen over the curve of the earth: a light 30 m up is visible from a deck 5 m up at about 18 miles, and the towers were as tall as the coast needed, low on cliffs, 30 to 60 m on flat shores.

Screw-piles and caissons

• Screw-pile lighthouses. For soft bottoms in shallow water, Alexander Mitchell's invention of 1838: iron piles with a broad screw blade at the foot, turned into the sand or mud by capstans, six or eight of them in a hexagon, with a cottage on top for the keeper and the lantern on the cottage's roof; cheap and quick, and 40 of them were built in the Chesapeake Bay, the Carolina sounds and the Florida keys from 1850, of which Thomas Point Shoal of 1875, still on its piles in the bay, and Drum Point, moved ashore, survive; the Florida reef lights, Carysfort (1852) and Sand Key, are skeleton towers of iron on screw-piles 30 m high that have stood through every hurricane.
• Caisson lighthouses. For deeper water and ice, from the 1870s: a cylinder of iron plates, 10 m across, was floated to the site, sunk on the bottom and filled with concrete, the "sparkplug" light, and the tower built on it; Duxbury Pier (1871) in Massachusetts was the first, and the Delaware Bay, New York Harbor and Long Island Sound have dozens. The pneumatic caisson, sunk with compressed air and men digging inside as at the Brooklyn Bridge, was used where the bottom was soft, at Fourteen Foot Bank in Delaware Bay in 1887, the first in a lighthouse.
• Crib lighthouses. On the Great Lakes, timber cribs filled with stone and sunk, with the tower on top, against the ice: Spectacle Reef in Lake Huron (1874), whose limestone tower was built in four summers on a crib in 3 m of water 17 miles from land, is the Great Lakes' Minot's Ledge.

The light: from oil to the Fresnel lens

Until the 1820s a lighthouse was an oil lamp, Argand's of 1782 with a hollow wick and glass chimney, in front of a silvered parabolic reflector, and a dozen of them around the lantern; Augustin Fresnel, a French physicist, in 1822 designed a lens of concentric rings of glass prisms that gathered the lamp's light from all directions and bent it into a horizontal beam, the beehive of glass that stands 3 m high in the first order and weighs 3 tons, made by Henry-Lepaute and Barbier in Paris and Chance in Birmingham, and the beam could be seen 20 miles; France fitted its lights at once, Britain from 1835, and the United States, whose lights under Stephen Pleasonton's Treasury were the worst in the world, only after the Lighthouse Board of 1852 took over and ordered them for every station. The lens was rotated by clockwork the keeper wound, with a curtain of flashes whose pattern, the "characteristic", was the light's signature; the oil was whale oil, then lard, then kerosene from 1870, then the incandescent oil vapour lamp of 1900, then electricity; the fog signal was a cannon, a bell, then the steam siren and the diaphone. The Fresnel lenses were taken out in the 20th century for rotating beacons and are the treasures of the lighthouse museums.

The keepers

A keeper's day was the lamp: fill it, trim the wick, polish the lens and the lantern glass, wind the clockwork, light it at sunset and put it out at dawn, stand watch through the night, and log the weather and the ships; the pay was 400 to 600 dollars a year in the 1850s, with the house, the boat and the garden, and the assistants less, and the post ran in families, wives and daughters serving as keepers when the men died, Ida Lewis at Lime Rock in Newport for 39 years, Abbie Burgess at Matinicus Rock, who kept the light through a storm of four weeks at 17 in 1856; at a rock light the keepers served a month on and a fortnight off, three men in a tower 4 m across, and the isolation, the storms and the boredom are the literature. The United States Lighthouse Service of 1910 replaced the Board, the Coast Guard took over in 1939, and automation, begun in the 1920s with acetylene and the sun valve, ended the keepers: the last civilian keeper retired in 1990 and the last American light to be automated was Boston Light in 1998, which keeps a Coast Guard keeper by act of Congress.

The numbers

• Oldest. Tower of Hercules, Spain, 2nd century; Sandy Hook, 1764, the oldest American light standing and lit; Boston Light, 1716 and 1783, the oldest station.
• Tallest. Jeddah Light, 133 m, concrete, 1990; Cape Hatteras, 64 m, the tallest brick; Skerryvore, 48 m, the tallest rock tower; Île Vierge in France, 82.5 m, the tallest stone tower.
• Rock towers. Eddystone 1759, Bell Rock 1810, Skerryvore 1844, Minot's Ledge 1860, Wolf Rock 1869, Bishop Rock 1887, St George Reef 1892, Fastnet 1904.
• American lights. About 1,500 built; about 700 stand; 132 in the collection; the Coast Guard keeps about 400 active, most with LED beacons.
• Fresnel lens. First order, 3 m high, 3 tons, visible 20 miles; six orders down to the sixth at 45 cm for harbours.
• Cape Hatteras move. 4,800 tons, 880 m, 23 days, 1999, 12 million dollars.
• Minot's Ledge. 1,079 blocks, 130 working days in five years, 300,000 dollars, 1860.

Versions and theories

• Lighthouses were built by the keepers. By engineers and contractors under the Board, with the Army's Corps of Engineers designing the hard ones; the keepers came after.
• The stones were laid underwater. They were laid at low tide on rocks that dried, in the hours available, by men who landed from boats; nothing was laid under water, and the sea filled the joints.
• Lighthouses were painted for beauty. The stripes, bands and spirals were daymarks, so that a captain could identify the light by day, and each coast's pattern was fixed by the Board.
• The Fresnel lens was invented in America. By Fresnel in France in 1822; the Americans, under Pleasonton, refused it for thirty years as too expensive, and their lights were the worst in the world until 1852.
• The Minot's Ledge keepers rang the bell as the tower fell. The bell was heard in Cohasset through the night of 16–17 April 1851, and the two keepers' bodies were found on the shore; the tower fell before dawn.
• Lighthouses are obsolete. GPS has made them so for navigation, and the Coast Guard has given away hundreds to towns and preservation groups since 2000; about 400 in the United States are still lit, as aids that need no satellite.

The engineers who built the rock towers were the same profession that built the bridges and canals of the age, in how the Brooklyn Bridge was built and how concrete was invented, where Smeaton's hydraulic lime for the Eddystone begins the story of modern cement.

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