Census data is accessible in two forms on the US Census site: Tiger/Line Geographic Shapefiles and as Tabulated Data (CSV) from the census proper, including a range of demographic, housing, and economic data. Follow these steps to join these two data types to generate geolocated maps of this data in QGIS (for a slightly outdated, but very detailed step-by-step tutorial, go here):
- find and download the census regions Shapefiles you are interested in from the Tiger/Line site. Choose appropriate region and granularity – census blocks are the smallest geographical unit used by the US census. Make sure to download the tiger regions from the year that corresponds to the tabular data you are getting (i.e. 2010, 2000, etc.)
- find and download the Tabulated datasets you are interested in from the US census factfinder2 site. (Click on the “Advanced Search” tab; Click the “Geography” tab; Click the “Name” tab; Enter the Name of the Region you are interested in – “Wayne County, Michigan” for instance; In the “Geography Filters” Column pick the appropriate geographical unit – e.g. “block”. After all of this, it should give you a list of regions that meet the search criteria. Select the region(s) you want and press “Add”. Close the Geographies pop-up, and you should see all of the tabulated datasets for this region and geographical unit. Select the dataset you want to download and press “View.” Verify the data is what you want and Press “Download.” In the download dialogue box, check the “Data and Annotations in Separate Files” box and press “OK” to start the download. This will bring up one more dialogue window with a progress bar. Once the progress is complete, press “download” to finally download the Zip file.
- Follow this tutorial to prep and import the two files to QGIS and join them based on the appropriate geometryID column (e.g. the block ID #) – You may want to do some cleaning of the csv file to remove any unwanted columns and to ensure the geoID column data matches with the shapefile. Use the find/replace command in Excel (CTRL-F) to facilitate this work.