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How to Use Census Data in ArcGIS: Joining Data & Shapefile in GIS

This is a short how-to guide for accessing and using the TIGER/Line Shapefiles as well as joining data from the US Census Bureau to the TIGER/Line Shapefiles created by Census bureau.

Joining Data & Shapefile in GIS

GETTING STARTED
The instructions are for the 10.x versions of ArcGIS.
The data from American FactFinder should be downloaded and saved in a Microsoft Excel Workbook format. 

OPEN ARCMAP
Open ArcMap and add the TIGER/Line Shapefiles for the area of interest to the map using the “Add Data” icon or “File – Add Data – Add Data.”    

      
CREATING THE JOIN
Both the data file and the TIGER/Line Shapefiles contain fields that uniquely identify a geographic entity.  These fields are necessary for creating a join.  

In ArcMap, right-click on the TIGER/Line Shapefile that the data will be joined to. Select “Joins and Relates.”  From the submenu, select “Join.” 


A new screen appears where you select the field from the shapefile that will be used to join the data.  You want the field with the fully qualified geographic code.  In the 2010 shapefiles the field is GEOID10.  In later versions of the shapefiles, the field is GEOID.  The TIGER/Line Shapefiles technical documentation has more information on the record layouts and definition of each field.
 

The next step is to select the data file.  Use the browse (open folder icon) option to navigate to the data file.  This is the Microsoft Excel Workbook file you created.
The final step is to choose the field from the data table to base the join on.  The fully qualified geographic code in the American FactFinder data download is in a field named “GEO#id2” (ArcGIS changes the “.” from the original file to “#”).  You have two join options:  “Keep all records” or “Keep only matching records.”  Click “OK.”


SEEING THE DATA
ArcMap builds a relationship between the shapefile and the data file.  To see the data, open the attribute table for the shapefile by
right clicking on the shapefile name and select “Open Attribute Table.”  
 
The table now has the attributes from both the shapefile and the data table.  The data can be used to create thematic maps or for other analysis.  Multiple files can be joined to the shapefile.


REMOVING THE JOIN
Removing the data join is similar to creating the join.  Right-click the shapefile layer that is joined to the data to be removed.  Select “Joins and Relates.”  This time select “Remove Joins.”  Select the join to be removed or select “Remove All Joins.”