So the answer to this question varies over time. In the early United States after the revolution it wasn’t until months after election day that all the votes would be counted and the electoral college results transported to Washington.

Originally the president was inaugurated in March, because the framers knew it would take a while to determine the winner.

The advent of the telegraph in the mid-1800s made this considerably faster, and just in the nick of time; California had just become a state.

In 1860, the New York Times had the results of the election of Lincoln in the paper the following morning.

But it’s worth recognizing that until the 20th century the presidency wasn’t what it is now. The federal government was much smaller and people could just meet the president at events. The president didn’t control nuclear weapons and the average citizen didn’t get much of anything from the federal government.

For the sort of people who had a subscription to a major newspaper, they found out pretty quickly. For your average working person who didn’t follow the news or politics, it wasn’t nearly as front of mind as it is today for everyone.

Last, the rush to be first meant even into the mid-1950s newspapers still made routine mistakes occasionally. The famous example was “Dewey defeats Truman” in 1948, but there were other examples as well. So just because you found out didn’t mean you always found out correctly.

/u/lord_mayor_of_reddit answered how long it took for people across the US to know the result of presidential elections