According to the most recent publicly available U.S. Census data from the year 2000, the five most common last names in the United States are Smith, Johnson, Williams, Brown, and Jones. But what are the regional variations? While the Census Bureau breaks out each last name by race and ethnicity, it doesn’t provide a count by state. There are other data sources, however. In 2014 ran the numbers from their own database, and compiled the top three most common last names by state. With the exception of the Southwest states and Hawaii, the top few names nationwide tended to also dominate the state-specific rankings.

However, another way to uncover regional differences at the state level is to calculate the most distinctive last name by state. Using a methodology similar to the “Most Distinctive Obituary Euphemism for 'Died' in Each State” map, I calculated the difference between the state and national prevalence of each of the top 250 last names nationwide, based on Social Security Administration data. The highest value gives the last name that is most distinctive to that state.

By and large, the results are reflective of each state’s demographics and immigration history. In New England and Appalachia, Irish and English names dominate (Walsh, Sullivan, Payne). In the Midwest and Mountain States, German and Scandinavian names are common (Jensen, Snyder, Carlson). In California, Florida, and the Southwest, it's Latino names (Lopez, Hernandez, Gonzalez). New York and New Jersey’s Jewish communities also show up (Cohen, Schwartz, Hoffman).

To see the top five names for each state and for more about the methods and sources used to create this map, visit this post at