A second WebJam seems to have been made for August 2018, this needs to be added to this article.
The idea of a site-making competition was floating around at least since late August 2017, as seen in NeoMail Summer #4 - Web 1.0 Awards? when Melonking says that Neocities "needs [...] some sort of award. Something that is handed out yearly in a number of categories, like Best CSS work, Most Unique Idea, etc.", OwlMan would reply to the E-Mail by saying;
I like the sound of that, infact, only the other day I was talking to Jakeonline (Design Choices) about the same thing and how good it would be to do something like that, I would love to see something like this on Neocities!
The idea of WebJam was first made public by Project2 in September 2017, when they posted on their profile asking if people would be interested in a weekly site-making competition.
The WebJam website was made on the 23rd of September 2017 where it has a sleeping robot on. The site was updated later to make the robot bigger and to advertise SpookyJay's WebsiteJam, but apart from that there were no other noticeable updates.
The site was last updated on the First of October 2017.
I. The WebJam website https://webjam.neocities.org/ [Internet Archive, archive.is]
II. Project2's post https://neocities.org/site/project2?event_id=476680 [Internet Archive, archive.is] [Internet Archive, archive.is] [Internet Archive, archive.is] [Internet Archive, archive.is] [Internet Archive, archive.is]