Get the Shapefile for your county

(Note: in the screenshots below I went through Table P1 to get the map. The process is identical for P5. I trust that you will be able to handle this discrepancy without me having to recapture al the screenshots to rebuild this page with images that show “P5″ rather than “P1″ in the background.)
Before we leave this FactFinder page, grab some geographic data about your county.

Before we leave this FactFinder page, grab some geographic data about your county.

AFF will ask you to select data you want to map. Pick any link in the second row of data down in the table.

AFF will ask you to select data you want to map. Pick any link in the second row of data down in the table.

Be patient: it may take 5 minutes for the Census server to generate the map.

Be patient: it may take 5 minutes for the Census server to generate the map.

When it finally appears, the map should show graded colors for all tracts in your county. This is a choropleth map. And you can download the data!

When it finally appears, the map should show graded colors for all tracts in your county. This is a choropleth map. And you can download the data!

This download dialog-box looks a lot like the one for the CSV download. But at the bottom it offers the new option to download ShapeFile data. Choose that.

This download dialog-box looks a lot like the one for the CSV download. But at the bottom it offers the new option to download ShapeFile data. Choose that.

It takes a little while for the server to generate this new zip file.

It takes a little while for the server to generate this new zip file.

Once the map-data file is generated, you can once again specify the path and filename for saving it.

Once the map-data file is generated, you can once again specify the path and filename for saving it.

Save it into ~/soc393/census/. We will unzip and use this data later in the semester.

Save it into ~/soc393/census/. We will unzip and use this data later in the semester.

Here is a super-brief explanation of shapefiles:
1. Shapefiles contain geographic elements: either points, lines, or polygons.
Points might represent tiny local objects like fire hydrants.
Line-files are used to show linear things like roads, streams, powerlines.
Polygon-files are used to show things with surface area, like Census Tracts and whole counties.
Since all of these elements exist “in three-dimensional space,” they are often called spatial elements.
2. Each entity in a shapefile has an identifier tag, and it is linked to a database table where one of the columns is the same identifier tag. In this database, different features that might be associated with the spatial element are called attributes or, more specifically, spatial attributes. For instance, a Census Tract can be represented as a polygon, and that polygon (that spatial element) can have various attributes like the total population, the population of African-Americans, of Latinos, of Asians, of non-Hispanic Whites–in other words, we could take all the Tract-level Census data we collect and add it to the attribute table (the database) of the shapefile, so that we can do things like create maps based on the relative concentration of one ethnic group or another in the Census-Tracts of our county.