How Lighthouses Work

Lighthouses have been around since ancient Egypt. The Tower of Hercules, built by the Romans in northern Spain during the first century A.D., remains the oldest functioning lighthouse in the world [source: United Nations Educational, Scientific and Cultural Organization]. And as maritime trade expanded, so did the presence of lighthouses around the world, from China to Indonesia to Africa to Estonia. Famously, the Stevensons, a Scottish family of lighthouse engineers that counted author Robert Louis Stevenson among its progeny, built 97 lighthouses along the Scottish coastline and elsewhere [source: Bathurst].

Lighthouses first appeared in New England in 1716. In 1789, Congress created the U.S. Lighthouse Establishment to bring lighthouses under federal control. After first earning a second-rate reputation for the poor quality of its lighthouses, the United States became home to more than 1,000 lighthouses by 1900 [source: Ray]. And with more than 120 lighthouses, the state of Michigan possesses more lighthouses than any other state [source: Michigan State Housing Development Authority].

Wood fires were the earliest illuminants. As lighthouses proliferated, lamps powered by coal, whale oil, kerosene and other fuels became commonplace. One of the most novel lighthouse inventions, the Fresnel lens, came along in 1822 and used a network of prisms to magnify a small amount of light and cast a beam over distances of 20 miles (32.18 kilometers) or more. The lens was widely used across the pond, but under Stephen Pleasant, who oversaw lighthouses from 1820 to 1852, U.S. lighthouses were equipped with low-cost alternatives. Soon after the establishment of the Lighthouse Board in 1852, all lighthouses in the United States were equipped with Fresnel lenses.

In 1886, the Statue of Liberty became the first lighthouse powered by electricity, and served as a lighthouse in New York Harbor for 15 years. Most lighthouses had gone electric by the 1930s after access to electrical lines expanded. Electrical lines led to a series of inventions, including automated time clocks, devices to replace burnt-out light bulbs and improved radio communications technology, propelling lighthouses down the path toward automation [source: Michigan Lighthouse Conservancy].

Manned lighthouses had grown rare by the 1960s, when the Coast Guard implemented the Lighthouse Automation and Modernization Program. There were fewer than 60 manned lighthouses by the end of the decade. The modern lighthouse is a bare-bones structure comprised of an automated beacon atop a steel skeletal tower. Today, there is only one manned lighthouse in the United States.

What was the life of a light keeper like? Read on.

The lighthouses of the ancient world were manned by slaves and soldiers [source: Ray]. In Europe during the Middle Ages, monks and nuns staffed the structures. By the heyday of the late 19th century, most light keepers were professionals employed by agencies like the Lighthouse Board (later the U.S. Lighthouse Service), or the Trinity House, England's equivalent of the Lighthouse Service. Many light keepers were formerly fishermen, sailors, sons of light keepers or individuals with some other connection with the maritime field. Salaries were generally very low -- U.S. keepers earned $200 annually in the late 19th century, while Canadian keepers earned half that amount [source: Ray].

Typically, light keepers worked in two scenarios. The first, a "stag station," was a lighthouse manned by a head keeper and a few assistants who worked in shifts, spending long stretches away from their families. This was particularly common in offshore lighthouses. In the second scenario, a keeper lived with his family on the premises. With a few notable exceptions, light keepers were almost always men.

A light keeper's job required singular attention. Before automation, the scope of his responsibilities including refilling the oil in the lamps, changing and trimming the wicks, sounding the fog signal, cleaning the lens of soot and debris and otherwise keeping things tidy.

Officially, light keepers simply reported wrecks and hazards; life-saving endeavors were the province of the U.S. Lifesaving Service, a precursor to the Coast Guard. But in reality, light keepers were responsible for saving many lives [source: United States Coast Guard]. Ida Lewis, one of the few female light keepers in history, is probably the best remembered of this bunch. As the official light keeper for Lime Rock Lighthouse off the coast of Newport, R.I., between 1872 and 1911, Lewis personally rescued more than a dozen sailors from the water. These feats earned her a cover story in Harper's Weekly.

To increase efficiency, President Franklin Delano Roosevelt dissolved the U.S. Lighthouse Service in 1939 and brought its responsibilities under the purview of the Coast Guard. Most of the records from the period before 1939 have been lost except for log books kept by the light keepers themselves, Gales says. And, unfortunately, none of the light keepers from that era are still alive. "All you have now to talk, to get actual fact-based history, are some of the families that remain," Gales says [source: Gales].

Finally, let's take a look at five of the most interesting lighthouses in history:

The Pharos of Alexandria

First constructed around 270 B.C., in ancient Egypt and one of the Seven Wonders of the Ancient World, the Pharos of Alexandria is widely believed to be the first lighthouse in existence. It also might have been the tallest structure on the planet: Estimates claim the three-tiered lighthouses might have reached up to 450 feet (137.16 meters) tall. The beacon was a fire burning in an open cupola -- a small glass device -- that was reflected onto the water with a mirror, guiding ships into the port of Alexandria. An earthquake destroyed the structure in 1326 but undersea remnants of the lighthouse were discovered in 1994.

Eddystone Light

The environment around Eddystone Light in Plymouth, England was so inhospitable that this lighthouse had to be built four times. Henry Winstanley started construction on the first wooden structure in 1696 and, after he was captured and briefly imprisoned by the French, the lighthouse was lit in 1698. In 1703, the already damaged lighthouse was swept out to sea. The next iteration lasted from 1708 until it burned down in 1755. Next, esteemed engineer John Smeaton built a lighthouse with a broader base that lasted for 123 years, until a concerned Trinity House disassembled the lighthouse for fear that it would be destroyed in 1882. The same year, James Douglass used larger stones and a more precise design to build the lighthouse that stands today, 14 miles (22.5 kilometers) off the coast.

Boston Light

Established at the entrance to Boston Harbor on Little Brewster Island, Boston Light is a bookend of sorts for American light keepers. It was home to the first paid keeper, George Worthylake, who was assigned in 1716, and it also remains the only manned lighthouse in the country. Each year, the 8-mile (12.87 kilometer) Boston Light Swim, the oldest open-water swim marathon in the country, is held in the surrounding waters [source: Boston Light Swim].

Cape Hatteras Lighthouse

Measuring 208 (63.39 meters) feet tall, Cape Hatteras Lighthouse in North Carolina is the tallest lighthouse in the nation. It lords over the Outer Banks, a particularly precarious stretch of the Atlantic Ocean that has earned the moniker "Graveyard of the Atlantic" for the untold number of shipwrecks that have occurred there.

St. George Reef Lighthouse

Built between 1882 and 1892 on rocks a few miles off the coast of Crescent City, Calif., St. George Reef Lighthouse is believed to be the most expensive lighthouse ever built in the United States. The price tag? More than $700,000 [source: St. George Reef Lighthouse Preservation Society].