The following is a direct copy from the Wikipedia article on lighthouses. It is very comprehensive, and may help you understand why we had lighthouses, and why we still need them – because modern unmanned technology fails!
I have left all the webpage links and EDIT links intact in case someone has something to contribute to the article. It is a long article, but worth reading. never cease learning!
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Lighthouse
The lighthouse of Aveiro, west coast of Portugal
The Roman lighthouse at Dover Castle
A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses and used as an aid to navigation for maritime pilots at sea or on inland waterways.
Lighthouses mark dangerous coastlines, hazardous shoals, reefs, safe entries to harbors, and can also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and replacement by modern electronic navigational systems. Continue reading Lighthouse