The prime meridian is a
geographical reference line that passes through the Royal
Observatory, Greenwich, in London, England.
It was first established by Sir George Airy in 1851, and by
1884, most ships used it as the reference meridian on their
charts and maps.
In October 1884, 41 delegates from 25 nations met in Washington,
D.C., United States,
for the International Meridian Conference.
This conference selected the meridian passing through Greenwich
as the official prime meridian due to its popularity.