Mapping US Census Bureau Data With ArcGIS Online

The US Census Bureau collects a vast array of demographic and economic data on a continual basis. Much of that data at various scales is made available through tables that can be downloaded from their data.census.gov data portal.

The challenge with that data is that it is made available to the public in formats that are difficult to import into GIS software.

This tutorial describes how to create choropleths of demographic data from existing layers in ArcGIS Onlin, and how to create new layers by joining US Census Bureau tables with TIGER/Line shapefiles for state, county, and census tract boundary polygons.

data.census.gov

Living Atlas Layers

ESRI, the company that provides ArcGIS Online, provides data as part of the service they sell to their users. One set of data from a wide variety of sources is their Living Atlas of the World. One of those data sources is the American Community Sources.

One challenge with using Living Atlas layers is that they are oriented around mapping in ArcGIS Online with with limited capability for analysis or for customization of symbology. However, if all you need is a quick map and you're just looking for common variables, the Living Atlas may be what you need.

This example shows how to create a quick choropleth of median household income. Note that with aggregated income numbers, median is often used instead of a mean (average) because income is unually not evenly distributed across a population, and a handful of wealthy people can distort averages so they are not representative of the typical economic well-being of people living in a particular area. (Yates 2020).

Creating a Map With a Living Atlas Layer

You can get metadata on the source of the information in a layer by clicking on the ellipsis beside a layer and selecting Show Item Details. In this case, we find this data is actually provided by demographers at ESRI rather than the US Census Bureau.

Getting Metadata For a Living Atlas Layer

Organizational Layers

Users in ArcGIS Online are part of an organization. This organization is associated with the business, government agency, or educational institution that holds the ArcGIS license that you are using.

If you are part of an organization where someone has created a demographic data layer, you can create a map from that layer fairly easily. This is especially useful for data sets where you will be using analysis tools on the data, where you wish to control the symbology of the layer more carefully, or if you need a variable that is not available from a source like the Living Atlas.

Creating a Map With a Layer From Your ArcGIS Online Organization

You can get metadata on the source of the information in a layer by clicking on the ellipsis beside a layer and selecting Show Item Details.

Getting Metadata For a Layer

Finding A Location in Google Maps

There may be occasions where you want to find a location from an ArcGIS Online map in Google Maps, such as to find a neighborhood name or information about a neighborhood business.

  1. Use the Measure -> Location tool to find the latitude and longitude in ArcGIS Online.
  2. Paste those coordinates into the search bar in Google Maps.
Finding An ArcGIS Online Map Location in Google Maps

Mapping Downloaded Table Data

It is possible to map table data that you personally download from data.census.gov, although the process involves multiple steps that are fraught with potential points for failure. You will generally want to avoid this process unless absolutely necessary.

Download The Data Table

  1. Search for the data you want in data.census.gov. For this example, we will map median gross monthly rent from the American Community Survey.
  2. When the table displays, select Geography and select the geographic areas you plan to map. In this case, we choose counties in NY State.
  3. Download the table. It is provided in a .zip archive file which you should open using the Windows File Explorer or whatever .zip file extraction tool you have available on your computer.
  4. Copy the .csv file that has data in the name to your desktop and open that file in Excel.
  5. Remove the top row in the file so that there is only one header row in the table before the data rows start.
Downloading Table Data From data.census.gov

Add The Data As an ArcGIS Online Bubble Map Layer

  1. Create a new Map from your ArcGIS Online home page.
  2. Select Add, Add Layer From File with the .csv data file.
  3. When asked to Locate Features, look through the fields and make sure the column containing the names of your areas are marked accordingly. In this example, the geographic areas should be marked as County.
  4. Select the column to style the bubbles. In this case we need to choose the monthly rent column.
Importing and Geocoding the CSV File To Create a Bubble Map

Download a TIGER Polygon File

  1. Go to the TIGER Cartographic Boundary Files download page.
  2. Download appropriate file from the US Census Bureau's The 20m resolution files are good enough for a web map while being fairly small for quick upload. The download is a .zip file containing a shapefile of polygons you should save to your desktop.
  3. Add -> Add Layer From File with that downloaded .zip file.
Importing a TIGER Shapefile of Polygons

Joins

Thematic maps indicate what is where. Data downloaded from data.census.gov data is the what. For bubble maps of states or counties, ArcGIS Online can geocode the place names in the data to get where. But for choropleths, you need where polygons that represent states, counties, census tract, etc. boundaries that can be colored with the what data.

A join is an operation where two data sets are connected to form a single data set. There are two kinds of joins: spatial joins and attribute joins.

A spatial join joins two data sets based on a spatial relationship. In the animation below, data from a points data set (the join layer) is joined with a polygon geometries data set (the target layer) to create polygons with data from the join layer.

This type of join is useful for state data, where ArcGIS Online can geocode American FactFinder data state names into points, and that point data can then be joined with state boundary polygons to create choropleths.

Spatial Join

An attribute join connects two datasets based on common key values. This type of join is useful for county and census tract data, since ArcGIS Online cannot reliably geocode county or census tract names.

Attribute Join

Spatial Join the Bubble Layer To The Polygon Layer

Because we now have a polygon layer and a bubble layer, we can perform a spatial join.

  1. Click the Analysis icon on that polygon layer and select Summarize Data, Join Features
  2. Since the data points are already geocoded, you can use a spatial join with Choose a spatial relationship
  3. Click off current map extent so any features not currently displayed (like Alaska and Hawaii) are included in the output data
  4. Save the joined data under a meaningful name
  5. Show credits to make sure the operation will not use too many credits. State joins should use under one credit
  6. The join may take awhile depending on how many features you are joining. If the join takes longer than five minutes, the tool may have completed without notifying you. You can return to the home page, return to the map, and then add the layer from your content.
  7. Style the polygons based on the newly joined data variable
Creating a Choropleth Using a Spatial Join

Save and Share

Save the map under a meaningful name and share with everyone to get a link you can e-mail or submit for an assignment.

Note that you may get a warning message that one of your map layers also needs to be shared so the map is visible to everyone.

Sharing a Choropleth