This lovely 1864 hand-colored map depicts the states of Maryland and Delaware. The map includes a paragraph notation on the surveying of the boundary between Pennsylvania, Delaware, and Maryland, commonly called the "Mason Dixon Line." This line marked the geographical division between the Northern and Southern states at the outset of the Civil War.
Map by Alvin Jewett Johnson, courtesy Geographicus

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  • On October 18, 1767, the Mason-Dixon survey was completed. The resulting Mason-Dixon line is a boundary that set parts of the borders between Pennsylvania, Maryland, Delaware, and Virginia (today, West Virginia). The Mason-Dixon line is often recognized as the division between the U.S. North and South.

    This was not the original intent for the line. As a result of border disputes between the colonies of Maryland and Pennsylvania, Charles Mason and Jeremiah Dixon were asked to determine an official boundary. Mason was an astronomer with the Royal Observatory, Greenwich, in London, England. He used observations of stars to determine longitude. Dixon was a surveyor, also from England. Between the two, they slowly and accurately determined a boundary and marked it with stones. The Mason-Dixon line follows a latitude of 39 degrees and 43 minutes north of the Equator.

    The Mason-Dixon line runs for 375 kilometers (233 miles), and the survey took five years to complete.

  • Term Part of Speech Definition Encyclopedic Entry
    accurate Adjective


    astronomer Noun

    person who studies space and the universe beyond Earth's atmosphere.

    border Verb

    to exist on the edge of a boundary.

    boundary Noun

    line separating geographical areas.

    Encyclopedic Entry: boundary
    determine Verb

    to decide.

    dispute Noun

    debate or argument.

    latitude Noun

    distance north or south of the Equator, measured in degrees.

    Encyclopedic Entry: latitude
    longitude Noun

    distance east or west of the prime meridian, measured in degrees.

    Encyclopedic Entry: longitude
    north Noun

    direction to the left of a person facing the rising sun and the leading direction on a compass.

    recognize Verb

    to identify or acknowledge.

    South Noun

    loosely defined geographic region largely composed of states that supported or were sympathetic to the Confederate States of America (Confederacy) during the U.S. Civil War.

    surveyor Noun

    person who analyzes the specific boundaries and features of a piece of land using mathematical concepts such as geometry.