Data-Based Diagram of Similar US States

Diagram of relationships between similar US States

The State Similarity Index attempts to quantify how similar American states are to each other relative to other states. The index is a statistically-based way to measure this. It weighs equally five major aspects of states: their demographics, culture, politics, infrastructure, and geography. The methodology is exactly the same for each state.

The data from the State Similarity Index was used to cluster American states into different regions. Some unique states, like Alaska and Hawaii, are very difficult to group with other states. Therefore, it was necessary to make the largest regions still have a great deal of variation within them. This resulted in 6 distinct macro-regions: Northeast, Midwest, The South, The West, Alaska, and Hawaii.

However, it may best to look at states as a connected web, not as hierarchical clusters, since the data reveals the relationship of states to each other is more of a gradient than having clearly defined clusters. Therefore, a diagram was created to reveal more intricate linkages between states rather than simply grouping them into regions.

Hopefully, this graphic will help people understand the similarity of states relative to each other better than a traditional map, which only shows geographic adjacency. This suggests other political, cultural, demographic, and technological adjacencies that a physical map of the United States does not account for.

Downloadable graphic:


The logic of the connected web is as follows: each state is connected to its most similar state and also the next most similar state that is not more similar to the states more similar to the state. For example, the most similar state to Arkansas is Alabama. However, its next most similar states, Mississippi and Tennessee are all more similar to Alabama than Arkansas. The next state that is more similar to Arkansas than Alabama is Kentucky. Therefore, Arkansas is on a spectrum somewhere between Alabama and Kentucky.
In reality, the web would need to be three dimensional, since there are limits to what can be shown clearly on a two dimensional graphic. In order to fit all the connections on a two dimensional web, it was necessary to break some of the lines where there is significantly less similarity. For example, Utah is on a spectrum between Idaho and Colorado. However, since Utah is far different from Colorado, they are not connected.
Please keep in mind that just because some states are close to each other on this graphic, does not necessarily mean they are very similar to each other. For state specific questions, it is best the consult each individual state’s page on this site. Only the lines connecting states are meaningful, not their location on the graphic. For example, although West Virginia and Iowa are next to each other in the graphic, no lines are between these states, so no relationship is necessarily implied. The thicker the line, the closer the similarities between the states are.

Regional Breakdown

The West

Diagram of the United States West Region

In the West, the Rocky Mountain region spans between Utah and Colorado. Utah is an outlier since most of its people are Mormon. Colorado is more representative of the entire West region since it is not far different from the Pacific Coast or Southwest regions, so it connects to them. California has elements of both the Southwest and the Pacific Coast, so California and Nevada are connected.

The West region also connects to the unique states of both Hawaii and Alaska, since their most similar states are both part of the region. South Dakota and Montana are the most similar pair of states in the West and Midwest respectively, so this link connects the West to the rest of the United States.

The Midwest

Diagram of the United States Midwest Region

Two distinct clusters of similar states emerge in the Midwest: one region centered around the Great Lakes and another region centered around the Great Plains. In makes sense that Minnesota connects both groups together because it borders both the Great Plains and Great Lakes.

The Midwest is the only region that connects to three other regions in mainland United States. Missouri and Indiana are two Midwestern states that have more aspects of the Southeast region, since they are more conservative politically. Pennsylvania is a transitional state between the Great Lakes region and the BosWash region.

The South

Diagram of the United States South Region

In the South, the entire region is clustered around Alabama. Radiating out from the center are several outliers. Texas, Louisiana, Florida, and West Virginia are relatively unique, so they only connect to one other state. The states on the Atlantic Coast could be classified as a distinct region as well.

Oklahoma‘s geography has some characteristics of the Great Plains states, so it is linked with Kansas. Virginia borders the Northeastern state of Maryland, so it is no surprise that these states are linked together as well. While both states had once allowed slavery, Virginia joined the Confederacy, while Maryland stayed part of the Union.

The Northeast

Diagram of the United States Northeast Region

As for the Northeast, the sub-regions within this macro-region are not completely clear. While most geographers consider New England to be its own region, the Index finds that grouping just Vermont, Maine, and New Hampshire together might make more sense. They are much more rural, since are they are the only states not part of the BosWash megalopolis in the region.

The data clearly shows that Pennsylvania is the state most similar to the Midwest in the Northeast region. In addition, Maryland and Delaware are the most similar states to the South in the Northeast region. They are some of the few states that allowed slavery but stayed in the Union during the Civil War.

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