History 263
Fall 1999

Getting Started with the Great American History Machine (GAHM)

  1. Log onto WindowsNT
  2. Open the User Applications folder on the desktop and launch GAHM, the Great American History Machine (GAHM icon with U.S. map).
  3. Under File menu at top, select Open and then Data Set
  4. Open the file USA19TH.HMD and wait for GAHM to read map boundary files.
  5. There should be three scrolling-list boxes at the bottom of the screen. In the left-most box (titled data set) select the specific data set you wish to work with.
  6. In the middle scrolling-list box (titled topics) scroll down past the User Variables and Working Variables entries to the content-specific categories. Click on a category.
  7. The right-most scrolling-list box (titled variables) now shows the actual variables available. Choose a variable by clicking on it.
  8. Click the Map button to the right of the scrolling-list boxes. A county-level map of the United States for the variable chosen will be displayed, along with a brief MapKey explaining the color code of the map.
  9. To access a more complete legend for the map and a statistical summary of the mapped data, select the Options button at the bottom of the MapKey box. Note that by default, the History Machine divides the data into quintiles for mapping purposes. You may customize the map by changing the cut off points in the legend and then clicking on the OK button in the Statistics window.
  10. To zoom in on a particular area, move the cursor to the middle of the area and double click on the left mouse button.. To zoom out from a particular area, double click on the right mouse button. You can also go to the View menu.
  11. To identify the name and value of a particular county, move the cursor over it, hold down the shift key, and click once on the left mouse button.  
  12. To create your own user variable, click on Formulate on the toolbar. A Formula Edit Window appears. In this window, type a name for your new variable, followed by an equal sign, and the variable�s definition. You may use existing variable to help "build" new variables. Double-clicking on an existing variable in the variables scrolling-list box brings it into the Formula Edit Window. You may also use the Operator buttons. Operations include standard arithmetical expressions and a few special options, such as Maximum Value (mav), Minimum Value (miv), and Presence/Absence (pa).
  13. Once you have defined the formula for your variable, click on Evaluate in the Formula Edit Window.
  14. Your new user variable should now be listed in the variables scrolling-list box. To map the variable, highlight it and then click the Map button.
  15. Note that you may open up to five maps at a time and you can make maps zoom in tandem by using the Tether Views option under View.
  16. You may study a particular region, state(s), or group of counties in depth by using the Select Region option under the View menu once a nationwide map has been created. In the boxes at the bottom of the screen, indicate which areas you want to select for study and hit the OK button on the right. A new map highlighting the selected area will be generated and statistics for that area alone will be used to calculate the values for the MapKey.