2010. National Geophysical Data Center. This line shapefile shows lines of equal annual change (secular variation) in the horizontal component of the total field intensity of the Earth's ... National Atlas of the United States.
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2010. National Geophysical Data Center. This shapefile shows lines of equal annual change (secular variation) in the inclination of the Earth's magnetic field, derived from the Internatio... National Atlas of the United States.
2010. National Geophysical Data Center. This line shapefile shows lines of equal annual change (secular variation), in the total field intensity of the Earth's magnetic field, derived fro... National Atlas of the United States.
2010. National Geophysical Data Center. This line shapefile shows lines of equal annual change (secular variation) in the vertical component of the total field intensity of the Earth's ma... National Atlas of the United States.
2010. National Geophysical Data Center. This shapefile contains isodynamic lines (lines of equal total intensity of the Earth's magnetic field), derived from the International Geomagnetic... National Atlas of the United States.
2010. National Geophysical Data Center. This line shapefile shows lines of equal vertical intensity of the Earth's magnetic field, derived from the International Geomagnetic Reference Fie... National Atlas of the United States.
1999. Geological Survey (U.S.). This line shapefile portrays the major roads in the United States, Puerto Rico, and the U.S. Virgin Islands. The file was produced by joining the i... Geological Survey (U.S.).
1890. United States. Bureau of the Census. Relief shown by hachures.; Panel title.; At head of map: Eleventh Census of the United States.; Includes text and list of railroads. 56 x 75 centim... U.S. Bureau of the Census (Washington, D.C).
1894. United States. General Land Office. Relief shown by shading.; Shows roads, trails, railroads (proposed and contructed), U.S. land offices, and townships not subdivided.; Map shows org... General Land Office (Washington, D.C).
1914. Oklahoma Geological Survey. Shows rivers, county boundaries, county seats, roads and railway lines. 67 x 128 centimeters Scale approximately 1:633,600 General Map Collection. The Survey (Norman, Okla).