How Lighthouses Work

The History and Technology of Lighthouses

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.