"GIS is a computer technology that uses a geographic information system as an analytic framework for managing and integrating data; solving a problem; or understanding a past, present or future situation."

For more information about the geographical information system, please visit http://www.gis.com.

If you're interested in the 1921 Shelby County Atlas, click

http://digital.lib.uiowa.edu/cdm4/document.php?CISOROOT=/atlases&CISOPTR=810

 where you will also find many other Iowa county vintage atlases.