The series of citywide events, including a reenactment next year of the first so-called Reminder Day demonstration, are still in planning stages, to be unveiled this summer.
"The oldest library company in America - you can have no more distinguished institution taking a stand for LGBT history and its importance," said Chris Bartlett, executive director at the William Way LGBT Community Center in Center City, which is organizing the events.
Founded by Benjamin Franklin in 1732, the Library Company is the nation's oldest library and the only major colonial American library that survives virtually intact and is unaffiliated with a college or university. Now at 1314 Locust St., it has more than 500,000 items in its archives.
The single-room exhibit will be christened Friday evening with an opening reception and lecture by noted author David Halperin. It and others planned for larger venues across Philadelphia are meant to highlight gay cultural history.
"Here they are talking about a gay football player coming out," said retired Free Library of Philadelphia administrator John Cunningham, referring to the University of Missouri senior who could become the NFL's first openly gay player. His coming-out pronouncement over the weekend drew gasps in light of the sexual norms in locker rooms.
Cunningham, however, noted that courage was in perhaps higher supply at the 1965 demonstration - and each July 4 that followed until 1969, when the Independence Mall action was moved to New York City.
Ostracism or worse awaited those audacious enough to publicly identify themselves as gay, he said.
"Fifty years ago, you can imagine how courageous it was for these people to step forward," Cunningham said. "The discrimination against the community was" high.
The Library Company exhibit trains its lens on a distant era when poets such as Walt Whitman celebrated same-sex relationships and others enjoyed popularity despite gender-bending prose.
A particular treat awaits Whitman buffs: The Library Company's own 1860 third-edition printing of Leaves of Grass, an exceptionally rare piece, is on display for the first time in perhaps a decade. Leaves is among 100 exhibit items reflecting 19th-century cultural norms on sex.
"It was actually a golden age," King said.
A piece by the New York poet Fitz-Greene Halleck, a man dubbed "the American Byron," shows how.
Years after he had penned a highly intimate poem about his literary partner, Joseph Rodman Drake, the poem was included in an anthology that called Halleck one of the most popular authors of his time.
America had become more hostile toward gay culture by the 1950s and '60s, paving the way for decades of activism. But King said her exhibit offers at least one lesson: "History is very changeable."