It’s no question that 2020 has been a historic year for the U.S., but how it will affect the future remains to be seen.

In an effort to take stock of where this year fits into history so far, TIME asked historians nationwide to pick a moment in 2020 that stands out to them. We asked them what future historians will—or at least should—write about when they study the momentous year that is drawing to a close, and whether it signals a new chapter or turning point for America and the world.

Below is what the historians who spoke with TIME, as of early December, identified as the major milestones of 2020:

Feb. 5: The Senate acquits President Trump in his impeachment trial

Trump’s acquittal in his impeachment trial by the Senate on Feb. 5, 2020, is a really important moment both within American history and for what it says about Trump’s success at imposing an authoritarian style political culture on the Republican party. With only one contrary vote by [Utah Sen. Mitt] Romney, everyone else unanimous. You couldn’t ask for a greater legitimation of his political style.

Sen. Sherrod Brown wrote a really interesting op-ed in the New York Times saying his Republican colleagues were afraid and told him that they acquitted Trump out of fear, not because they really believed he should be acquitted. If you compare it to what happened to Nixon, the difference is you have this authoritarian personality that has managed to take hold.

For historical comparison, some of the other rulers who have done this successfully created their own parties or had leadership roles within their parties for years before they became head of state. Mussolini created his own party. Berlusconi was able to do this, he created his own party. But Trump’s achievement is even greater because the GOP has a very long history, and we only have two parties, and yet he was able to tame it and make it his own.

—Ruth Ben-Ghiat, Professor of History and Italian Studies at New York University