A "bellwether" is a sheep that leads the flock, wearing a bell around its neck to guide the rest of the herd. In politics, a "bellwether " is a political subdivision whose voting patterns often predict the outcome of a national election.
Out of the 3,144 counties or county equivalents in the United States, 19 have the distinction of being bellwether counties. This means that the county has predicted every presidential election accurately since 2008 AND has predicted at least 80% of the presidential elections since 1980. Most of these counties are located in the northern part of the country. Most of them are small in population.
This site offers a look at the 19 existing bellwether counties prior to the 2024 Presidential Elections between Vice President Kamala Harris and former President Donald Trump.