Which meridian was chosen as the prime meridian at the 1884 International Meridian Conference?

The Greenwich meridian was chosen as the prime meridian at the 1884 International Meridian Conference.

The conference met in Washington, D.C., in October 1884 to establish a common reference for longitude and international timekeeping. Delegates selected the meridian passing through the principal instrument at the Royal Observatory in Greenwich, England, as zero degrees longitude.

The choice reflected the widespread use of British nautical charts and the importance of the British merchant fleet. Twenty-five nations participated; the final vote was 22 in favor, one against, and two abstentions. France abstained and continued using the Paris meridian in some contexts for a time.

Modern geodesy uses the International Reference Meridian, which differs slightly from the historical Greenwich line because satellite-based coordinates use Earth-centered reference systems. In everyday maps and time discussions, however, Greenwich remains the familiar prime-meridian reference.