The completion of the first North American telegraph line between Washington, D.C. and Baltimore on May 24, 1844, introduced a technology that could transmit time signals at a large fraction of the speed of light. On September 28, 1850, the United States adopted two primary meridians of longitude for officially use: the Greenwich Meridian (through the old Royal Observatory at Greenwich, England) for all nautical and international use, and the Washington Meridian (through the old United States Naval Observatory in Washington, D.C.) for more accurate astronomical and domestic use. The completion of the first telegraph line across North America, on October 24, 1861, allowed time signals from the Naval Observatory in Washington, D.C. to be transmitted across the continent.