“We wanted to explicitly recognize the association with LGBT history,” she said. “In most cases, the designation of the historic districts in which the buildings already exist did not recognize this history.”

Since its start, the commission has expanded its mandate toward recognizing buildings for what happened in them, not just their presence on the landscape, with a number of other designations, among them Louis Armstrong’s house in Queens, a landmark since 1988.

A year ago, the commission created a historic district in Harlem, citing the “rich social, cultural and political life” that went on there as well as the architecture. It includes the home of the ragtime composer Scott Joplin and the national headquarters for the March on Washington in 1965.

The six most recent sites were chosen based on their contribution to gay history. Recognizing more than architecture “is really important,” said Andrew S. Dolkart, co-director of the LGBT Historic Sites Project, which recommended sites for the LGBT designations.

“In general, it’s really important that preservation move beyond just works of architecture, not to denigrate that — I’m an architectural historian,” he said, adding, “We really need to recognize places of cultural and historical significance.”

Giving the six buildings landmark status would put documentation about them in the commission’s files that would be taken into account if owners sought to make changes to the outside, Ms. Carroll said. That information, she said, “would guide our thinking” and could prove especially important for facades that “might not have been seen as typical or traditional in that particular historic district.”