25th meridian west from Washington

The 25th meridian of longitude west from Washington is a line of longitude approximately 102.05 degrees west of the Prime Meridian of Greenwich. In the United States of America, the meridian 25 degrees west of the Washington Meridian defines the eastern boundary of the State of Colorado, the western boundary of the State of Kansas, and the western boundary of the State of Nebraska south of the 41st parallel north.

On January 1, 1861, the Act Admitting the State of Kansas to the Union defined the western boundary of the new state as the 25th meridian of longitude west from Washington. This rendered the western portion of the Territory of Kansas unorganized. Thirty days later on February 28, 1861, the Act Organizing the Territory of Colorado defined the eastern boundary of the new territory as the 25th meridian of longitude west from Washington. The creation of the Colorado Territory moved the western boundary of the Territory of Nebraska south of the 41st parallel north east to this meridian. These boundaries on the 25th meridian of longitude west from Washington remained when Nebraska became a state on March 1, 1867, and Colorado became a state on August 1, 1876.

Latitude and longitude uniquely describe the location of any point on Earth. Latitude may be simply calculated from astronomical or solar observation, either at land or sea, interrupted only by cloudy skies. Longitude, on the other hand, requires both astronomical or solar observation and some form of time reference to a longitude reference point. John Harrison produced the first precise marine chronometer in 1761.

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