Attendees at the Women’s March on Washington on Saturday. (Amanda Voisard for The Washington Post)

Some descended on Washington’s Mall very early, and some joined later. Some stood in long lines outside Metro stations to get downtown. Others walked a long way.

The signs were almost all homemade. Many were clever, channeling humor and whimsy (“There will be hell toupee,” “Things are so bad even introverts have to protest”), as well as anger, determination and commitment.

And the crowd got so big that it broke into tributaries, marching in different directions. The tributaries eventually joined up to form a mighty stream of protest. No matter how much President Trump and his administration try to lie and spin, every objective indication is that far more people showed up to register dissent over his rise to power than to celebrate it.

It was a diverse crowd in many ways, more white than African American and Latino but with a fair representation across racial lines. It tilted young but included many among the middle-aged and the senior set. A couple of older demonstrators I ran into carried signs asking why they had to be protesting about the same injustices after all these years (in language too colorful to include here).

For many, it was a multi-generational day, a family affair: grandparents, parents and children, some in strollers. Women predominated, but a large minority was male, and a fair number of men carried signs suggesting, in various formulations, that real men, good men, supported the rights of their sisters and wives and mothers.

The Women’s March was decidedly about women, their rights and the demand that they not be denied. But it was at least as much a message to Trump and to the country: Less than 24 hours after the new president took the oath of office, hundreds of thousands of Americans came together to say that they would not stand by in silence if the new administration threatened basic freedoms or the advances of the past eight years, and the last 50.

The message of the Washington March was echoed by large crowds that gathered in cities and towns across the country. In their different ways, the marchers were saying that they would not be cowed into silence or demobilized into a sullen difference. They were, as the marchers chanted at various points (recalling a favorite Barack Obama shout), “Fired Up.”

Washington’s was a jubilant gathering — jubilant in large part because so many were so grateful to each other for showing up in such large numbers. Those who had spent Jan. 20 in gloom spent Jan. 21 experiencing a sense of relief: In the face of the political troubles to come, they would have allies and friends. The passion, energy and commitment in politics have shifted decisively. Goodbye tea party. Hello Accountability Party — although I am sure someone will eventually come up with a better name.

The anger and dismay over Trump was a dominant emotion, and judging by the signs, its sources were multiple: his attitude and behavior toward women especially, given the theme of the day, but also Russia’s role in the election and Trump’s bromance with Vladimir Putin. Many signs poked fun or expressed alarm at Russia. One, channeling an old statement from Trump supporter Sarah Palin, read: “I can see Russia from here.”

There were many signs in support of voting rights and against voter suppression, some support for the Affordable Care Act (“I Obamacare about You” read one), and for the Black Lives Matter movement and gay rights. There were loud calls for the defense of free speech and freedom generally. If Trump didn’t talk about freedom in his inaugural address, this crowd picked up the slack.

And while there were signs that registered continued support for Hillary Clinton (one displayed the popular vote count and Clinton’s nearly 2.9 million vote advantage over Trump), the messages were overwhelmingly forward looking. There was an acceptance of the reality that Trump is president but a stout rejection of who he is and what he stands for. That included expressions of a desire to drive him from office, with the inevitable breakout of “Hey hey, ho ho, Donald Trump has got to go” chants.

The politics of the next few months and years will depend a great deal on whether the energy displayed on Saturday is sustained through the hard work of political activism. I can imagine skeptics reading this and saying one day of protests will be very easy for Trump and the Republican Party to absorb (even if one can imagine Trump’s fury at not getting even a day’s peace).

But there is reason to believe this was not a one-off. First, there was not a single march in Washington but demonstrations all over the country. As the tea party showed, change comes from local actions coordinated nationally. There is clearly a large national base of opposition, community by community.

Second, the reaction to Trump is unprecedented. No other president faced such a wave of rallies immediately after he took office. No other president so quickly mobilized so many people against him. Trump really is special.

Third, the march here (and such evidence I have seen suggests this was true elsewhere) was strikingly nonsectarian. There were not people pushing very narrow ideological agendas or political subgroups insisting that they and only they had, in old left parlance, “the right line” on the future. Different parts of the anti-Trump coalition were generally happy to reinforce one another’s messages.

Finally, Trump’s election jarred many progressives and moderates from quiescence. If these marches were for women and against Trump, they were also marches against complacency. That may have been their most important message.