The city of Toledo, the seat of Lucas County, Ohio, sits in the northwestern corner of the state along the Michigan border. Like so many border counties, Lucas is home to more than a few interstate rivalries, most notably a clash between University of Michigan fans and Ohio State fans so entrenched that one local shop is divided down the middle to accommodate both fandoms.

In fact, 180 years ago, both Michigan and Ohio claimed a strip of territory including Toledo due to a dispute known as the Toledo War. Ohio won that border tussle — which, unforeseeable at the time, was very bad news for Hillary Clinton.

Like most urban counties, Lucas County favored Clinton by a solid margin — though not solid enough to put Ohio in the Democrat’s column. However, had the county been part of Michigan, as was nearly the case long ago, Clinton’s 35,000-vote margin of victory would have been enough to flip Michigan in her favor.

For those who did not support President Donald Trump, the 2016 election attracted new ire to the Electoral College, which handed Trump 306 electors to Clinton’s 232 even though she won the popular tally by nearly 3 million votes. But most diatribes against the Electoral College fail to account for a curious nuance to the age-old system: The results are largely determined by arbitrary state borders that, in some cases, were drawn before the United States was even a country.

As an experiment, TIME examined the results for all 3,108 counties in the continental U.S. and ran several simulations to see how the results would have been different if those state lines were slightly adjusted — without moving a single actual voter, just the state he or she calls home. In the most striking of those scenarios, one can flip the results of the 2016 election by reassigning just three counties to neighboring states: Lucas County, Ohio; Mercer County, N.J. and Lake County, Ill, as demonstrated below.

Of course, states don’t redraw their borders after every decennial Census, the way they redraw and reapportion congressional districts. Nor is there an easy mechanism for a county to secede. (North Carolina and South Carolina have been arguing over a small sliver of territory for 20 years.) But when the presidency is at stake, it’s worth remembering that the nation itself is made up of archaic boundaries that lead to unpredictable outcomes.

Methodology

Because a state’s number of congressional representatives is related to its population, changing a county from one state to another can actually alter the number of electoral votes a state has. To account for this, this app recalculates the number of electoral votes per state with each move. For example, moving Lake County adds an electoral vote to Wisconsin while taking one from Illinois. These figures are calculated using 2010 Census population figures in accordance with the official government apportionment methodology.

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Write to Chris Wilson at chris.wilson@time.com.