Well, I was there. A 15-hour day trip from Richmond, Virginia; crowded trains and buses, trudging pre-dawn freezing streets, standing in the bitter cold to gaze at video screens depicting an event happening about a mile away, laughing, cheering, smiling broadly at strangers (often to no effect, since my scarf was tightly wound up to keep my nose warm), finally arriving back sore, tired, hungry and frozen through.

Wouldn’t have missed it for the world.

Just as it’s no surprise that the inauguration was a big event, there’s also no secret about the reason: America loves a celebration, and Barack Obama is the most exciting new president that anyone can remember. But it’s interesting to note some reasons why Tuesday was even bigger than Obama’s popularity might suggest.

First of all, there’s geography. Washington and its environs are not representative of the country at large; they are much more heavily Democrat, and this, of course, was mostly a Democrat crowd. The District of Columbia voted more than 90% for Obama, and he comfortably carried Maryland and Virginia as well — the first Democrat to win Virginia since 1964.

Local Democrat strength is partly due to the black vote, and African-Americans were well represented in the crowd. DC itself has long been a black-majority city, but there are now many in the suburbs as well with the growth of the black middle class — not to mention large black populations in nearby cities such as Baltimore, Richmond and Philadelphia.

That means big inauguration events are likely to be Democrat. It’s significant that the previous record attendance was not from recent times, when Republicans have mostly dominated, but from Lyndon Johnson’s inauguration in 1965 — the first Democrat, incidentally, to whom blacks had anything much to be grateful for. (He also sent many of them to die in Vietnam, but that mostly came later.)

Quite aside from race and politics, there’s also something about this part of the country that makes the historic nature of Obama’s presidency resonate. Directly opposite the hotel where I’m staying, at the edge of Richmond Airport, is a plaque marking the spot where the main Confederate defence lines crossed the Williamsburg road.

This is the land over which Americans fought and killed one another over the racial question; to end what Lincoln, in perhaps the greatest of inaugural addresses, called “the bondsman’s 250 years of unrequited toil”. Living in Idaho, for example, would not give one quite the same stake in the advent of a black president.

But many people had traveled larger distances to be there, and that made class a factor as well: only those of a certain income level are likely to take enough time off work and bear the costs of getting to Washington for an event like this. Historically, those people have been mostly Republican, but Democrats in general, and Obama in particular, have been gaining ground among the well-off; that translated to more visitors in the Mall.

Finally, there’s the importance of youth. The youth vote was crucial to Obama’s success, and although all ages were represented on Tuesday, it stands to reason that a candidate depending on the under-30s will draw more people to an event like this than one relying on the over-60s. Members of John McCain’s core demographic, for their own sake, would be well advised not to spend hours standing outside in sub-zero temperatures.

So the shifting trends of geography, class and age probably gave an impression of even greater significance to an event that already had significance in plenty.