The State Similarity Index attempts to quantify how similar states are to each other relative to other states. The index is a statistically-based way to measure this. 20% of the index is based on culture. 16.66% of a state’s culture score (3.33% of the overall State Similarity Index score) is based on the historical background of a state, including Native American history, colonial history, and Civil War history. The following paragraphs explain which aspects were used in the calculation.
Native American Cultural Group
The Native American tribes in the United States encompass a diverse range of cultures, shaped in part by their unique environments. For example, the Plains tribes, who resided in the grasslands, adopted a nomadic way of life, utilizing horses for hunting and portable teepees for shelter. On the other hand, the Southwest tribes, residing in the deserts, established permanent settlements constructed from adobe, and practiced agriculture, cultivating crops such as corn, beans, and squash. In Alaska, the Sub-Arctic tribes relied heavily on fishing, and their houses were built with ample insulation to protect against the harsh cold climate.
Source: Smithsonian Institution
States were categorized based on the following Native American cultural groups that were historically in their state:
Basin, California, Hawaiian, Northeast, Northwest, Plains, Plateau, Southeast, Southwest, Sub-Arctic
Native American Linguistic Group
There is also great linguistic diversity between the indigenous people of the United States, comprised of many different language families that are unrelated to each other. Interestingly, the linguistic groups of Native Americans do not always align neatly with their cultural groups. For example, while the Cherokee are part of the Southeastern cultural group, the Mohawks belong to the Northeastern group. However, both tribes speak Iroquoian languages.
Source: Smithsonian Institution
States were categorized based on the following Native American linguistic groups that were historically in their state:
Algonquian, Athapascan, Austronesian, Aztecan, Caddoan, Californian, Coahultecan, Eskimo, Iroquoian, Kiowa, Muskhogean, Salishan, Shapwailutan, Siouan, Timucuan, Tonkawan, Tunican, Uchean, Yuman, Zunian
Date of Statehood
Since the United States started out as a group of British colonies, these early settlements were situated along the Atlantic Coast, since they were more easily accessible. As a result, the oldest states are generally in the Eastern portion of the United States. In 1821, Missouri was the first state completely to the west of the Mississippi River. In 1863, West Virginia was the last state east of the Mississippi to gain statehood, since it separated from the rest of Virginia during the Civil War. By then, Oregon and California were already states. With the exception of Alaska and Hawaii, landlocked states in the Western United States were the last to gain statehood, since they developed the latest. Arizona and New Mexico were admitted as states in 1912.
Source: Encyclopedia Britannica
States were categorized into the following groups by year of statehood:
1785-1800, 1800-1815, 1815-1830, 1830-1845, 1845-1860, 1860-1875, 1875-1890, 1890-1905, 1905-1920, 1920-1935, 1935-1950, 1950-1965
The United States began as a territory ceded by Great Britain after the Revolutionary War. However, over time, the country expanded its territory. In 1803, the United States nearly doubled its size through the Louisiana Purchase from France. Subsequently, Florida was ceded to the United States by Spain, and the independent Republic of Texas joined the country. In 1848, after the Mexican-American War, Mexico ceded California and many Western states to the United States. Alaska was later purchased from Russia in 1867 and Hawaii was annexed in 1898. These acquisitions and annexations significantly shaped the territorial landscape of the United States, leading to its present-day geographical boundaries.
Source: US Department of the Interior
States were categorized into the following groups by which country they belonged to before their territory was acquired by the United States:
France, Great Britain, Hawaii, Mexico, Russia, Spain, Texas
Historical Status of Slavery
Prior to the Civil War, the issue of slavery in the United States was characterized by a stark divide between states. While some permitted slavery, others did not. Southern states, with economies reliant on agriculture, heavily relied on enslaved labor to carry out the arduous work. In contrast, northern states generally opposed slavery based on religious and moral grounds. Notably, religious interpretations were often invoked in the South to justify and defend the institution of slavery, further deepening the divide on this contentious issue.
Slavery Allowed, Slavery Abolished
Allegiance during Civil War
During the Civil War, states that permitted slavery typically aligned with the Confederacy, while states that prohibited slavery remained part of the Union. However, there were exceptions to this pattern, including Missouri, Kentucky, West Virginia, Maryland, and Delaware, which were border states situated between the North and the South. However, during the Civil War, a considerable portion of the United States territory did not have statehood or were part of other countries at the time.
Confederate, Union, Neither
Historical Status of Segregation
Even after the Civil War, racial segregation persisted in many states, with laws mandating the practice of separating society based on race. However, some states completely outlawed segregation, while in others, local communities were given the option to implement or reject it. This was particularly evident in school systems until the landmark court case, Brown v. Board of Education, in 1954. Generally, states that had allowed slavery prior to the Civil War also had systemic segregation practices. However, it’s important to note that while Northern states may not have legislated segregation, elements of their society still practiced it in more subtle forms.
Required, Neither – Local Option, Neither – Not Legislated, Outlawed
Historical Status of Interracial Marriage
Before the Loving v. Virginia court case, interracial marriage was not allowed in many states. The Supreme Court eventually ruled that banning interracial marriage was unconstitutional. A few Northern states like Vermont and New Hampshire have never banned interracial marriage. Even during the 1940s, most states in the South and the West did not allow interracial marriage. This even included California and Oregon, two states that nowadays are well known for being liberal.
Source: Loving Day
States were grouped into the following categories by the date when interracial marriage was allowed:
Banned Before 1865
Banned Before 1900
Banned Before 1957
Banned Before 1967