NavList:

The Washington meridian was created in the early 1850s because astronomical longitudes were considerably less accurate than longitudes determined by ground surveying and also those determined by telegraph signals. Boundaries defined by legislation could be determined accurately only relative to a standard meridian on US land. As soon as transatlantic cables were reliable starting in 1866 (after a brief capability in 1858), there was no need for a separate Washington meridian. Thus the Washington meridian was actually required by geographic/geodetic science for less than 16 years. Other "national" (and increasingly "nationalist") meridians were rendered obsolete even earlier. The conferences in 1883 and 1884 were formalities, opportunities for a little horse-trading, international parties, and also a necessary process to overcome entrenched bureaucracies.

Frank Reed