In the midst of Donald Trump’s big week (clinching the GOP nomination, tweeting about tacos), the candidate took a minute to breathe new life into a beloved conspiracy theory: JFK was killed and there’s something we just don’t know.

Trump referenced the president’s killing to go after then-opponent Ted Cruz, but his remarks also called attention to the fact that the JFK-death truthers are alive and well—along with believers in BigFoot, Area 51, and those who wonder about the 1966 “death” of Paul McCartney.

These theories predate the internet, but many have found new, and robust, homes there. The vast world of conspiracy websites and forums across all corners of the web has brought hundreds of thousands of “creative thinkers” together—and, over the course of the last twenty years, a whole online ecosystem has sprung up to support them and their theorizing.

Vocativ analysts dug deep into the underbelly of the beast to track the rise of the conspiracy theory web, when it started, and where it’s blossoming.

Unsurprisingly, there was a major boom in conspiracy theory sites after 2001 and the terrorist attacks on World Trade Center. Several sites were even specifically created for the purpose of 9/11 truthing, like the Let’s Roll 9/11 Forum. The topic is also featured prominently on several of the biggest conspiracy theory sites out there, like DavidIcke.com and Before It’s News.

Within the conspiracy theory community, certain influencers wield vasts amount of power. Take Alex Jones, David Icke, and Lisa Haven, three of the biggest names in “truthing.” They’ve garnered fame for espousing their beliefs in government corruption and the Illuminati, among other fun topics. While Icke and Haven both run eponymous websites, Jones spreads his brand of conspiracy across multiple platforms, including Infowars and Prison Planet.

And it’s not just their own wacky theories that these celebrity truthers offer up to the Internet. An important aspect of these niche realms is the sense of community they offer. David Icke’s forum gives 100,000 like-minded thinkers the opportunity to chat in various forums, where they’re free to discuss their highly speculative thoughts, like how Jeb Bush’s presidential race departure can be traced back to—surprise!—what really happened on September 11.

Though the term “conspiracy theory” harkens to 9/11 truther theories, false flags, and government mind control, it turns out that there’s actually a sizable community of natural health nuts that turn to Natural News as a source for advice on wellbeing. Like the effectiveness of hemp oil as a cancer treatment (who knew?!). Staffed by a team of 20 writers, the site has a whopping 1.8 million Facebook fans.