It was Pennsylvania when things started to get crazy.
We were in a bar somewhere on Capitol Hill, where a crowd of young Washingtonites were huddled round a television. And whenever the networks called a state for Obama, they started cheering, even when it was such a solidly blue state as Massachussets or Vermont. (Logic dictates there must be plenty of Republicans in this town somewhere, but I didn't seem many of them last night.)
But it was when they called Pennsylvania that things really took off. This was the state McCain had bet everything on, this was one he couldn't afford to lose - and within mere minutes of the polls closing, there it was, standing safely behind Barack Obama.
But still people didn't allow themselves to believe. By 9pm I was telling anyone who was foolish enough to come within three feet of me that this thing was over, that Obama would win and win big, but my American friend was having none of it. "He might just scrape past 270," he shrugged. But that was it.
When we got in a cab across town, the first words spoken by the Pakistani driver - I'm pretty sure he hadn't even asked us where we were going - were, "Is he winning?" He switched on the radio, where we heard that Fox were calling Ohio for Obama. "Ah, that is good," he said. "But he still needs Florida, I think."
By the time we found another television, somewhere on U Street, Obama had 204 in the electoral college, and the polls had yet to close on the west coast. That, best I could tell, made President Obama an inevitability.
But no-one was saying it. There were painful memories of 2004, and no-one wanted to jinx a possible victory.
So when, at 11pm, the magic words appeared on the screen, the place exploded. People were screaming, hugging, high fiving strangers. One of two girls at the back of the bar who looked like they hadn't noticed it was election day asked the room what had just happened, and received a unanimous cry of, "He won!". They looked bored. Maybe they were the ones who voted for McCain.
Meanwhile the world outside had collapsed into a spontaneous street party. Cars were hooting, people were yelling, and the crowd was spilling into the road. At the corner of 14th and U hundreds were dancing alongside four guys with steel drums. About a dozen had climbed onto a bus shelter that, contrary to popular expectations, didn't collapse. One guy was sitting on a traffic light. Another was in a tree.
And the police let it all happen. I'm pretty sure some of them even joined in the hooting.
In the middle of the dancing there was one guy in a suit, looking staid and calm and, frankly, lost. My American friend suggested we stick a McCain badge on his back, just to see what happened. But no-one wanted that on their conscience.
It was after the victory speech that everyone decided to march on the White House. Its staff had cleverly arranged to have some building work going on, so we could only get so close, but that didn't stop thousands of people from showing up with the express intention of making as much noise as they possibly could. "Let's wake the old guy up!" someone was yelling.
Two guys with a cardboard cut out of the President Elect found themselves besieged by people wanting to pose with it for a photograph. Another guy - and I make no claim to understand this - was running around in his underwear, looking for all the world like he'd just forgotten to get dressed for his midnight jog.
"You Brits do realise this isn't going to change US foreign policy even one little bit?" said my American friend, never to one to accept victory without declaring a defeat.
But it didn't matter. The inevitable disappointment could wait. America had voted for President Obama, and that was all we needed to know.