A gap in the technology
The LAN party was born in a specific and temporary gap. Through the 1990s and early 2000s, three-dimensional graphics grew rapidly more complex while consumer network speeds did not keep pace. The result was a class of games — fast, twitch-based, latency-intolerant — that were essentially unplayable over the internet connections most people had, while slower strategy games did fine. Communications technology was being outpaced by graphical power, and the LAN party is what filled the hole.
Doom's release in December 1993 is the usual starting gun. It supported up to four players over a local area network, and the emphasis is on local: to play Doom against your friends, you and your friends had to be on the same network, which in practice meant being in the same building. So people lugged their computers to a friend's house, wired into their network, and played. That is the whole origin. There was no cultural movement behind it, just an engineering constraint and a strong desire to shoot each other.
The hauling
It is worth being concrete about what this involved, because the physical absurdity is the defining feature. A 1990s gaming PC was a full tower and a CRT monitor — the monitor alone being a heavy glass object roughly the size and weight of a small television. Participants disconnected their machines, carried the towers, monitors, keyboards, mice, and cables to a central location, and set everything up again on borrowed tables, connecting through a network switch. Then they did it in reverse at the end.
The payoff was a local connection running at speeds far beyond anything available to an average internet user, which meant lag-free play. That is the transaction: hours of physical labour and a strained back in exchange for latency low enough that a rocket launcher felt responsive. People did this repeatedly, voluntarily, for years, which tells you exactly how bad the alternative was and exactly how much the games were worth to them.
The golden era
The late 1990s and early 2000s are generally treated as the LAN party's peak, and the games did the defining: Doom and Quake first, then StarCraft and Counter-Strike, which gave the format a competitive spine and a reason to run all weekend. Events scaled from a friend's living room to rented halls to large conventions, and sessions stretched from hours into days.
The imagery is consistent enough to be a genre: sweaty rooms, tangles of cable, empty bottles of Mountain Dew, glowing CRTs in the dark, people who have not slept. What was actually happening in those rooms was social. Players shared strategies, formed rivalries and alliances, and made friendships that outlasted the games — the LAN party was as much a gathering as a competition, and the fact that it required physical co-presence meant the community that formed was made of people who had been in a room together.
Why it ended, and what went with it
Broadband killed the LAN party by solving the problem that created it. Once home connections could sustain a fast shooter at acceptable latency, the entire rationale for carrying a CRT across town evaporated. Online play delivered the same games with none of the labour, plus opponents at any hour rather than whoever could make it on Saturday. Nobody chose to end the era; it simply stopped having a reason.
What is easy to miss is that the thing which disappeared was not the gaming but the co-presence — and the co-presence had been carrying weight nobody had asked it to carry. When your opponents are in the room, the social norms of being in a room apply: you can see the person you just beat, and you have to keep sitting next to them. The internet delivered the games and removed the room, and much of what online multiplayer culture has struggled with since is a consequence of that removal. The LAN party was a workaround for a bandwidth limitation, and it accidentally produced a set of social conditions that the technology's improvement quietly took away.