Name an L.G.B.T.Q. landmark. Perhaps it’s the Stonewall Inn on Christopher Street in Manhattan. Maybe it’s Castro Camera, Harvey Milk’s shop in San Francisco, or even the Coral Sea Islands, where activists started their own micronation to advocate the legalization of gay marriage in Australia.

All three places appear on Queering the Map, a digital atlas that invites L.G.B.T.Q. people to tag any point on earth with an anonymous message describing what the location means to them.

But the interactive website, which was started in 2017 by Lucas LaRochelle, a 27-year-old artist and digital designer, isn’t your average guide of L.G.B.T.Q. historical places. Even if some pay homage to recognizable stomping grounds, the entries tell distinctly personal stories about the many different locations where people have experienced important queer moments in their lives.

Mx. LaRochelle, who is nonbinary and uses they and them pronouns, has described the map as an archive of the places where L.G.B.T.Q. people have not been welcomed by all, but have always existed.

Mx. LaRochelle originally devised the visual project as a class assignment while they were a student at Concordia University in Montreal, where they live. This month, the site surpassed half a million submissions, with the United States alone accounting for more than 180,000 of the markers. Mx. LaRochelle said the milestone was a testament to the “absolutely lifesaving” potential of digital platforms like Queering the Map, which can provide L.G.B.T.Q. people with comfort and solidarity that can be difficult to find in the real world.

But it didn’t happen all at once. Mx. LaRochelle contributed the site’s first few entries: the tree at which they first encountered their partner and later had a life-changing realization about their nonbinary gender identity, the shipping container in the woods where they met with a secret lover in their youth.

Then others found the site — first friends, then strangers. Hundreds of pins were added to locations around the world, then hundreds of thousands.

“There’s definitely a style in how a Queering the Map post reads: It’s often emo, sometimes funny,” Mx. LaRochelle said. “It’s fascinating to me the way that the confessional mode of writing in the first couple of stories that I added has persisted.”

When Thomas Dai first learned about Queering the Map, he wondered what messages he might find in his hometown. As Mr. Dai zoomed in on Knoxville, Tenn., he recognized the buildings and bends in the road but saw the familiar places inhabited by unfamiliar memories. In a park at a local university, someone had proposed (successfully) to a boyfriend. On a street downtown, a transgender man held hands with another man for the first time.

Mr. Dai, a 31-year-old writer, was especially moved by the messages posted at his former high school. Although he was out as gay when he was a student there, he didn’t feel connected to the L.G.B.T.Q. community, he said.

“It was humbling to realize that there is queer history everywhere,” said Mr. Dai, who lives in Boston. When he added a pin of his own, he marked the address of his apartment in Qingdao, China, where he lived for a year with his partner and another queer friend — a place and time “surrounded by gay energy,” he said.

Casey Ross, a lecturer on geographic information systems at the University of Pennsylvania, used Queering the Map as course material in an urban-studies class she taught last fall. She said she wanted to show that maps weren’t just tools for navigation: They could also be media of outreach, storytelling and “disruption.”

“To have a project that explicitly maps nonheteronormative experiences is, in many ways, directly contrary to a lot of the political movements that we’re seeing now that are trying to force this idea that queerness is bad or a disease or harmful,” Ms. Ross, 35, said.

Internet projects typically have short life spans, and Mx. LaRochelle has learned in the past six years how time-intensive and expensive it is to tend a continuously growing archive with a small team of stewards.

Mx. LaRochelle established guidelines in the early days of Queering the Map, after the website was spammed with pro-Trump messages. Now, when someone submits an entry, Mx. LaRochelle or one of the site’s few dozen volunteer readers must review it before it is posted. Because the small team can approve only so many messages at once, a large backlog is not unusual. Everyday maintenance work — reading submissions, laughing or crying at said submissions, reviving the site when it crashes — is “less sexy,” but essential to the project’s livelihood, they said.

Mx. LaRochelle is also busy refitting the digital project into the physical world. They designed an immersive exhibition, “Sex, Desire and Data,” to look as “if you put Queering the Map in a box, shook it up, then had it spiraling around a physical environment.” Mx. LaRochelle plans to debut the exhibition at the PHI Center in Montreal on Aug. 1, then tour across Canada and the United States.

Mx. LaRochelle attributed the project’s longevity to the spectrum of queer experiences it documents.

“If it’s happened once before, it can happen again,” they said. “That’s true for both joyous experiences and horrific experiences, which is why it’s so important to document our collective history in all its configurations.”