On November 5, 1605, the House of Lords was supposed to have been blown up by a group of Roman Catholic conspirators who were disappointed that the newly-crowned King James had not relaxed the anti-Catholic policies of his predecessor, Queen Elizabeth. Had the plot succeeded, James would have been killed at the State Opening of Parliament, along with a good many other English grandees. But the plot was exposed, and the principal conspirators, including Guy Fawkes, who was found guarding 36 barrels of gunpowder that had been placed in the House of Lords, were all arrested, convicted, and executed.

“A late 17th or early 18th-century report of the plot.” Wikipedia.
Since that time, the Fifth of November has been celebrated as a triumph of British Protestantism against the wicked forces of papistry. To this day, it serves an excuse to throw a stuffed “Guy” (or even a pope) onto a bonfire, or at least set off fireworks (I lived in London once, and can attest to this). I assume that the anti-Catholicism of the celebration has been downplayed in recent years, and that the fifth of November is simply the British equivalent of Hallowe’en – an occasion of autumn revelry.

“A contemporary engraving of eight of the thirteen conspirators, by Crispijn van de Passe. Missing are Digby, Keyes, Rookwood, Grant, and Tresham.” Wikipedia.
I have always been curious why the Fifth of November fell out of favor in the American colonies. Why don’t we celebrate it here anymore? Why did the Irish custom of Hallowe’en take off in from the nineteenth century? Apparently George Washington found it embarrassing. As he wrote in 1775:
As the Commander in Chief has been apprized of a design form’d for the observance of that ridiculous and childish custom of burning the Effigy of the pope—He cannot help expressing his surprise that there should be Officers and Soldiers in this army so void of common sense, as not to see the impropriety of such a step at this Juncture; at a Time when we are solliciting, and have really obtain’d, the friendship and alliance of the people of Canada, whom we ought to consider as Brethren embarked in the same Cause. The defence of the general Liberty of America: At such a juncture, and in such Circumstances, to be insulting their Religion, is so monstrous, as not to be suffered or excused; indeed instead of offering the most remote insult, it is our duty to address public thanks to these our Brethren, as to them we are so much indebted for every late happy Success over the common Enemy in Canada.
Alas, such consideration was not enough to win the French colonists to the cause of Revolution (thus does Canada exist today!), but apparently it had a permanent effect.
But as I wrote before, the casting of Guy Fawkes as a sort of anarchist freedom fighter has been one of the more remarkable transformations I’ve ever witnessed.