Putting Native American Voters on the Map: Using Cadastral Data to Geocode Non-Traditional Addresses

Putting Native American Voters on the Map: Using Cadastral Data to Geocode Non-Traditional Addresses

This post is part of a series of articles written by 2019 Summer of Maps Fellows. Azavea’s Summer of Maps Fellowship Program is run by the Data Analytics team and provides impactful Geospatial Data Analysis Services Grants for nonprofits and mentoring expertise to fellows. To see more blog posts about Summer of Maps, click here.

Native Americans have the lowest voter turnout by ethnic group. An estimated one-third of eligible Native Americans are not registered to vote, and according to Demos, Native American turnout is anywhere from 5 to 14 percentage points lower than non-Native American turnout. This gap reflects a long history of marginalization. Native Americans were not allowed to vote nationwide until the passage of the 1965 Voting Rights Act, and even then, until 1975, many states continued to deny the right to vote to people living in “unorganized counties,” a population that was disproportionately Native American.

Chart showing that Native American voters have lower turnout rates than many other races.
Voter turnout among races, 2008

Montana is no exception to this pattern. In Montana, overall voter turnout in 2016 was 74 percent. For Native Americans, that number was 59 percent. Despite this twenty point gap, Native Americans have played an increased role in recent elections.  In 2006, Senator Jon Tester credited the Native American vote for his razor-thin victory. While Native Americans only comprise seven percent of Montana’s population, they remain Montana’s second-largest racial population and are the fastest-growing demographic in the state, comprising 10 percent of new births in 2017.

Given this context, together with the Forward Montana Foundation, we set out to determine accessibility to polling places in Montana, with a particular focus on Native Americans. It was immediately apparent that in addition to policies that limit Native American turnout, because many Native Americans do not have traditional voting addresses, they also face unique geographic challenges that compound their decreased voter turnout.

Forward Montana Foundation logo

What are the challenges to mapping Native American voters?

  1. Many states restrict voting to those with a traditional formal address. A 2017 North Dakota law garnered attention when it required voters to have IDs with a traditional address format, which disproportionately impacted Native American voters. 
  2. Nontraditional addresses cannot be geocoded using traditional USPS reliant geocoding software, meaning that we cannot even locate where many Native Americans live.
  3. There is significant evidence showing that polling location matters. When Forward Montana worked to move a university polling place, from a spot over two miles from campus and not accessible by bike or bus, to campus, they saw a 194 percent increase in turnout. This question of accessibility is particularly salient in the context of rural states with large Native American populations. According to a 2017 Native American Voting Rights Coalition survey, 32 percent of voters in South Dakota said that distance to the polls was a limiting factor in their decision on whether or not to vote.

However, without an understanding of where people live, it becomes difficult to allocate resources, including polling locations. This is the premise that has led to the rise of The National Tribal Geographic Information Support Center (NTGISC) or “Tribal GIS,” a network that seeks to apply GIS technology to Native American communities. The first step in understanding Native American voting patterns in Montana is physically putting Native Americans on the map.

What is a Cadastral Survey?

A Cadastral Reference System (from the Latin root Cadastre, meaning public record or survey). According to Congressional mandate, these Public Land Survey Systems (PLSS) include information on ownership, tenure, area, use, and value, and are managed by the Bureau of Land Management (BLM). The Land Ordinance of 1785 enabled the federal government to use money generated from the sale of Western Territories to pay off debt incurred from the Revolutionary War. In order to sell the land, the government first undertook a comprehensive survey of over 1.5 billion acres of land that is still in existence in states west of Pennsylvania. The Northwest Ordinance of 1787, in turn, updated the PLSS to create rectangular surveys that facilitated the transfer of federal lands to private citizens, and what we now refer to as Cadastral data.

Map showing Lake County, Montana cadastral system, consisting of small squares of land.
Map of Cadastral system in Lake County, Montana

In 1998, Montana began the five-year process of creating a Geographic Coordinate Database, or a digitized survey database. This database is primarily pulled from the Cadastral Survey but is also supplemented by thirteen other layers from both federal and state-level data.

In 2014, the Montana State Library (MSL) took over management and publication of Montana’s Cadastral National Spatial Data Infrastructure (CadNSDI). Since its inception this database has proven to be a unique asset for the state, generating nearly $10 million, and providing local, county, and state government with easily accessible records.

Map of Montana showing the locations of each geocoded voter.
Montana voters geocoded in this project. Many voters were unable to be geocoded, particularly on tribal lands.

How do we use Cadastral data to locate Native American voters?

In order to match Section Range addresses to their respective Cadastral area we had to:

  1. Download the County Cadastral data from the Montana State Data Clearinghouse.
  2. Format Cadastral shapefile and Voter data in the same way. In our case this meant using R to concatenate Section/Range/Township columns into one column, separated by spaces, with every component preceded by a corresponding letter. It looks like this: concatenated cadastral data code
  3. Left join the Cadastral shapefile to voter data by this new unique ID. This means that every voter is now matched to their respective Cadastral polygon.
  4. Aggregate voter count per Cadastral polygon so that we now know how many voters fall into each Cadastral polygon.
  5. Create random points based on the number of voters within each Cadastral polygon using spsample.

While this does not give us a precise address location, it does give us an approximation within an average ten-acre area. Meaning that for the purposes of mapping average distance to polling locations, we can still identify patterns around polling location and race, just with slightly less precision.

Does Cadastral data improve our ability to map Native Americans?

We started by geocoding all 670,000 Montana voters. 95 percent of voters geocoded successfully, but the missing 5 percent of voters account for nearly 40,000 voters, of which, over 20 percent were located using Montana’s Cadastral Reference System. The average Native American population for a county in Montana is 6 percent, the average Native American population for the counties geocoded using Cadastral data is 13 percent. Meaning that Cadastral data is twice as likely to geocode Native American voters than straight forward geocoding.

What does this mean?

Montana is unique, and currently, there are few states with comparable databases where this process would be replicable. That being said, Montana has shown that creating Cadastral Databases is profitable and a worthwhile investment. There are more and more applications for this data that are coming to light — geocoding Native American voters with non-standard addresses is yet another innovative application. As states look to ensure equitable access to the polls, they will need to determine where low-turnout communities live. Cadastral Data provides new opportunities to put Native American voters on the map.

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