Wikidata knows of 9,770 lighthouses. Put every one on a map and light it, and the world's coasts draw themselves: thick and bright around Scandinavia, Britain and New England, thin and dark along much of Africa and Asia. Some of that is the sea, and some of it is who wrote the lights down.
Lighthouses are the most hopeful buildings we have: a tower put up on the worst rock on the coast so that nobody else has to die there. The Romans built them, the Victorians built them by the thousand, and now, with satellite navigation in every wheelhouse, we mostly keep them for love. Wikidata, the free database behind Wikipedia, records 9,770 of them with a position, and 6,546 with a year they were built or first lit.
This page puts them all on one map, counts them by country and by the length of each country's coast, follows the building boom decade by decade, and lists the oldest and the tallest. It is also a study of a record. Sweden alone has 2,555 of the lighthouses, 26% of the world's total, because a national list of Swedish lights has made its way into Wikidata almost light by light. Other countries with long, dangerous coasts barely appear. I will try to keep the two stories apart.
Switch the map to night and each lighthouse becomes a small lamp. Where they crowd, the coast glows: the Swedish and Finnish skerries, the Danish straits, the Channel, the Atlantic coast of the United States and the Great Lakes. Click any light for its record. You can colour the lights by when they were built, search for a light or a country, and turn the base map, hill shading and names on and off under Map layers.
Lights: 9,770 Wikidata items that are lighthouses (or a kind of lighthouse) and have coordinates, after removing 39 keepers' houses, barrack blocks and modern replicas. "When built" is the earliest inception date in Wikidata, which for some lights is the first light on the site rather than the present tower; 3,224 lights have no date. Lights more than 5 km inland from the sea coast are marked as lake and river lights. Heights in Wikidata were extracted without their units; see the notes in each record. Sources: Wikidata (CC0); Wikipedia contributors, List of tallest lighthouses (CC BY-SA 4.0); Natural Earth. Base map tiles © Esri.
Lighthouses are ancient, but most of the ones on the map are Victorian or younger. Of the 6,546 dated lights, only 144 were built before 1800. Then the industrial century arrives: iron, steam, cheap glass and the Fresnel lens, and maritime trade that needed every headland lit. Outside Sweden, new lights went from 103 in the 1820s to 376 in the 1870s, and stayed above three hundred a decade until the First World War. The United States built most in the 1870s (96).
Lighthouses built per decade, 1700 to today
6,546 dated Wikidata lighthouses by the earliest inception year, by country. The 2020s are only part way through. Hover a bar.
After 1910 the curve outside Sweden falls away: about 337 new lights a decade from 1850 to 1909, about 97 a decade from 1970 to 2019, a fall of 3.5 times. The good sites were taken, and the job of the lighthouse was changing. Lights were automated through the twentieth century, keepers left (in Britain the last of them came off duty in 1998), and satellite navigation, fully working from the mid 1990s, took over much of the work of finding a ship's position. New lights now tend to be small, unmanned beacons, and Wikidata rarely bothers with those.
Sweden tells a different story, or rather its record does. Sweden's 2,555 lights are nearly all dated, and they peak in the 1940s, with 326. From 1930 to 1969 Sweden supplies 70% of all dated new lights in Wikidata. Their recorded heights are small (a median of 8.9, against 16.0 for lights built elsewhere from 1850 to 1909, most of them in metres) and 89% have no Wikipedia article at all. These look like the small automatic lights that lit the Swedish archipelagos in the twentieth century, recorded because someone loaded a full national list. Elsewhere the same kind of light is simply missing.
By raw count, the top five are Sweden (2,555), the United States (923), Finland (794), Canada (473) and the United Kingdom (468). But a country with more coast needs more lights, so I also divide each country's sea lights by the length of its coast, measured on Natural Earth's 1:10m map: the outline of the country, minus every border it shares with a neighbour. The world has about 921,367 km of coast at that scale and 9.4 lights in Wikidata per 1,000 km of it.
Lighthouses by country
Top 20. Per 1,000 km: sea lights only, for countries with at least 1,000 km of coast and 10 sea lights (55). Hover a bar.
Per kilometre of coast, Sweden (341 per 1,000 km) and Finland (126) are far ahead, then Tunisia (85), whose 118 lights also look like a single import, and Germany (71). France (48), Spain (47) and the United Kingdom (39) sit together a little lower. At the bottom are countries with vast, island-strewn coasts: Canada has 2.9 per 1,000 km, Russia 1.2 and Indonesia 0.2. Indonesia certainly has more than 12 lighthouses; Wikidata does not.
The same sum for states, provinces and counties picks out the most crowded stretches of coast. All of the top ten are in Sweden and Finland, led by Västra Götaland on the Skagerrak, with 71.9 lights per 100 km of coast. Outside Sweden and Finland, the densest are Lower Saxony (13.8), on the shallow, shifting Wadden Sea, and Connecticut (12.9), where Long Island Sound is lit like a street.
Lights per 100 km of coast
The top 20 regions with at least 150 km of coast and 15 sea lights. Click a row to see it on the map.
The oldest date in Wikidata belongs to a lighthouse that is long gone: the Pharos of Alexandria, one of the Seven Wonders, dated 278 BC and brought down by earthquakes in the Middle Ages. The oldest that still stands, and still shines, is the Tower of Hercules at A Coruña in Galicia, a Roman tower dated AD 100. The Romans also left the Dubris Pharos inside Dover Castle (dated AD 200), still standing though long dark. Then come the medieval towers: Hook Head in Ireland (1300 in Wikidata, a date that looks rounded to a century), Kõpu in Estonia (1531), the Lanterna of Genoa (rebuilt 1543) and Cordouan in the Gironde (1615).
The oldest dated lighthouses in Wikidata
Years are Wikidata's inception dates. Whether a tower still stands is not in Wikidata's record: I marked the best known by hand, and say "not checked" where I could not be sure. Click a row to see it on the map.
Treat the old dates with care. Wikidata usually gives the year a light was first shown on the site, and old towers were often rebuilt on the same spot: the Genoese Lighthouse at Constanța is dated to the Genoese era but the tower is from 1860, and the Planier light off Marseille is dated 1326 though the present tower went up in 1959. Many early dates are rounded to a century.
For height I use Wikipedia's list of tallest lighthouses, which gives 28 traditional towers of 60 m or more, measured from the ground. The tallest is the Île Vierge lighthouse off Finistère, 83 m of granite, finished in 1902. 16 of the 28 are stone, granite or brick, and 11 are from the nineteenth century or earlier.
The tallest lighthouses
Tower height in metres, from Wikipedia's List of tallest lighthouses. Hover a bar; click to see it on the map.
Wikidata has a height for 4,066 lighthouses, but the extract I worked from kept the numbers and lost their units. Of the 26 towers in the Wikipedia list that I could match, 19 have a Wikidata height in metres and 1 (Cape Hatteras, 210) in feet. So on the map each record shows the Wikidata number with a warning, and the ranking uses the Wikipedia list only.
Wikidata's coverage of lighthouses is very uneven. Some countries' lights arrived in bulk from a national list, many of them without an English name or a Wikipedia article: 96% of Sweden's lights have at most one Wikipedia article, as do 91% of Finland's and 83% of Tunisia's, and 970 Swedish lights have no English label at all. Other countries are covered light by light, article by article, by volunteers: in the United States only 16% of lights lack a second article. And some coastal countries have no lighthouse in Wikidata at all, among them Greenland, Nigeria, Kenya, Ecuador and the United Arab Emirates.
How bare are the records?
Share of each country's lighthouses with at most one Wikipedia article, for countries with at least 40. High shares suggest a bulk import. Hover a bar.
So read the map twice. Its bright coasts are where the sea is busy and dangerous, and where lighthouse lists have found their way into open data. Europe holds 62% of the lights; Africa 5%, South America 3%. The dark coasts are not empty of lights. They are empty of records.
A lighthouse map is a map of danger, of trade and of whoever wrote the lights down.
Lighthouses. Every Wikidata item that is an instance of lighthouse or one of its subclasses and has coordinates, through the QLever service: 11,614 rows, one item per row and value, giving 9,810 items. I removed 39 keepers' houses, barrack blocks and replicas and 1 item whose position is recorded as unknown, leaving 9,770. Where an item has several inception dates (44) I use the earliest. Labels are English; 1,799 lights (18%) have none and are shown by their Wikidata number.
Countries and coasts. Each light is placed in the Natural Earth 1:10m country it stands in, or the nearest within 30 km for lights on rocks offshore; 97 lights further out take Wikidata's country. Natural Earth's map units are used as they are, so Greenland, Puerto Rico and the Faroes count on their own (I merged Åland into Finland). A light more than 5 km inland from the sea coast is a lake or river light (1,075, mostly on the Great Lakes and the Swedish and Finnish lakes) and is left out of the per-coast figures. Coast length is the part of each 1:10m country or region outline not shared with a neighbour, measured on the ellipsoid. Coastlines are fractal: at this scale fjords and skerries are smoothed, so the lengths compare countries fairly but are not the "true" length of any coast.
Oldest. Dates are Wikidata's inception years, unchanged. Wikidata does not say in this extract whether a tower still stands; I marked the 17 best known of the oldest lights by hand from their published histories and the Wikipedia list. Tallest. Heights and years from Wikipedia's List of tallest lighthouses (revision 1306705349), which follows the Lighthouse Directory's definition of a traditional lighthouse.