Alcatraz Island Lighthouse
E17238
Alcatraz Island Lighthouse is a historic beacon on Alcatraz Island in San Francisco Bay, notable as the first lighthouse built on the U.S. West Coast and a key aid to navigation for ships entering the bay.
All labels observed (2)
| Label | Occurrences |
|---|---|
| Alcatraz Island Lighthouse canonical | 2 |
| Alcatraz Island Light | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T138138 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: Alcatraz Island Lighthouse Context triple: [Alcatraz Island, hasFacility, Alcatraz Island Lighthouse]
-
A.
Great Point Light
Great Point Light is a historic lighthouse located at the northern tip of Nantucket Island, Massachusetts, guiding vessels through the surrounding coastal waters.
-
B.
Alcatraz Island
Alcatraz Island is a small rocky island in San Francisco Bay best known for its former maximum-security federal prison, which once held some of America’s most notorious criminals and is now a popular historic site and tourist attraction.
-
C.
Sankaty Head Light
Sankaty Head Light is a historic lighthouse on the eastern shore of Nantucket, Massachusetts, known for guiding ships along the treacherous waters off the island since the mid-19th century.
-
D.
Big Red Lighthouse
Big Red Lighthouse is a historic, bright-red navigational beacon at the channel entrance to Lake Michigan in Holland, Michigan, and a well-known local icon.
-
E.
Portland Head Light
Portland Head Light is a historic and picturesque lighthouse located on Cape Elizabeth’s rocky coast near Portland, Maine, and is one of the most photographed lighthouses in the United States.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: Alcatraz Island Lighthouse Target entity description: Alcatraz Island Lighthouse is a historic beacon on Alcatraz Island in San Francisco Bay, notable as the first lighthouse built on the U.S. West Coast and a key aid to navigation for ships entering the bay.
-
A.
Great Point Light
Great Point Light is a historic lighthouse located at the northern tip of Nantucket Island, Massachusetts, guiding vessels through the surrounding coastal waters.
-
B.
Alcatraz Island
Alcatraz Island is a small rocky island in San Francisco Bay best known for its former maximum-security federal prison, which once held some of America’s most notorious criminals and is now a popular historic site and tourist attraction.
-
C.
Sankaty Head Light
Sankaty Head Light is a historic lighthouse on the eastern shore of Nantucket, Massachusetts, known for guiding ships along the treacherous waters off the island since the mid-19th century.
-
D.
Big Red Lighthouse
Big Red Lighthouse is a historic, bright-red navigational beacon at the channel entrance to Lake Michigan in Holland, Michigan, and a well-known local icon.
-
E.
Portland Head Light
Portland Head Light is a historic and picturesque lighthouse located on Cape Elizabeth’s rocky coast near Portland, Maine, and is one of the most photographed lighthouses in the United States.
- F. None of above. chosen
Statements (48)
| Predicate | Object |
|---|---|
| instanceOf |
historic structure
ⓘ
lighthouse ⓘ navigational aid ⓘ |
| associatedWith |
Alcatraz Island
ⓘ
surface form:
Alcatraz Federal Penitentiary
United States Lighthouse Service ⓘ |
| bay | San Francisco Bay ⓘ |
| category |
Buildings and structures in San Francisco Bay
ⓘ
Lighthouses in California ⓘ Transportation infrastructure in San Francisco Bay Area ⓘ |
| constructionMaterial |
concrete
ⓘ
reinforced concrete ⓘ |
| country |
United States of America
ⓘ
surface form:
United States
|
| currentTowerCompleted | 1909 ⓘ |
| distinction | oldest operating lighthouse on the U.S. West Coast ⓘ |
| function |
guides ships into San Francisco Bay
ⓘ
warns of hazards around Alcatraz Island ⓘ |
| heritageStatus | listed as a contributing structure to the Alcatraz Island National Historic Landmark ⓘ |
| lightCharacteristic | flashing white light ⓘ |
| locatedIn |
Alcatraz Island
ⓘ
California, United States ⓘ
surface form:
California
San Francisco Bay ⓘ San Francisco ⓘ
surface form:
San Francisco, California
United States of America ⓘ
surface form:
United States
|
| locatedOn | rocky outcrop of Alcatraz Island ⓘ |
| maintainedBy | United States Coast Guard ⓘ |
| managedBy | United States Coast Guard ⓘ |
| marking |
gray lantern
ⓘ
white tower ⓘ |
| near |
Golden Gate Bridge
ⓘ
surface form:
Golden Gate
Port of San Francisco ⓘ
surface form:
San Francisco waterfront
|
| openToPublic | no ⓘ |
| originalConstructionCompleted | 1854 ⓘ |
| ownedBy |
United States government
ⓘ
surface form:
United States federal government
|
| partOf |
Alcatraz Island
ⓘ
surface form:
Alcatraz Island National Historic Landmark
Golden Gate National Recreation Area ⓘ |
| purpose | maritime safety ⓘ |
| region | West Coast of the United States ⓘ |
| replaced | original 1854 lighthouse tower ⓘ |
| role |
historical landmark
ⓘ
symbol of maritime history of San Francisco Bay ⓘ |
| significance |
aid to navigation for ships entering San Francisco Bay
ⓘ
first lighthouse on the U.S. West Coast ⓘ |
| towerShape |
square tower with gallery and lantern
ⓘ
tapered square tower ⓘ |
| viewableByPublic | yes ⓘ |
| visibleFrom |
Port of San Francisco
ⓘ
surface form:
San Francisco waterfront
ferries crossing San Francisco Bay ⓘ |
| yearFirstLit | 1854 ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: Alcatraz Island Lighthouse Description of subject: Alcatraz Island Lighthouse is a historic beacon on Alcatraz Island in San Francisco Bay, notable as the first lighthouse built on the U.S. West Coast and a key aid to navigation for ships entering the bay.
Referenced by (3)
Full triples — surface form annotated when it differs from this entity's canonical label.
this entity surface form:
Alcatraz Island Light