For kids and communities across America, prom night is both an enduring rite of passage and a sign of the times. This April, TIME commissioned photographer Gillian Laub to document this ritual in a journey that would take her across the country to Georgia, Missouri, Arizona, Oregon, New York and Massachusetts. In the resulting photo essay, “Last Dance,” Laub captured the bittersweet anticipation and excitement surrounding the annual tradition through a series of striking portraits of teenage prom attendees.
“Last Dance” is, in many ways, the culmination of a 10-year project for the New York City based photographer. One of the schools that appears in the essay, Montgomery County High School in Mount Vernon, Ga., first appeared on Laub’s radar when she traveled there in 2002 to photograph its homecoming festivities, then segregated by race, on an assignment with SPIN magazine. Seven years later, she returned to photograph Montgomery County High School’s prom, still segregated by race, for a project that was published by the New York Times magazine.
That would be the last time Montgomery County High School held a segregated prom, and Laub returned again this April to photograph students getting ready for just the third integrated event in the school’s history. “Naturally the first prom I photographed for the TIME essay was Montgomery County High School,” Laub says. “I wanted to follow the only biracial couple attending the prom. Only three years earlier they wouldn’t have been allowed to be each other’s dates.”
The word “prom” first appeared in 1894 in the journal of an Amherst College student going to a prom at Smith College nearby. In the century since, prom has become a distinctly high school tradition, a last chance for classmates to party together, before post-graduation plans send them in different directions. Today, as Laub’s pictures show, getting ready for prom plays as big a role as the dance itself; it plays out to big business, too. A 2012 survey predicted families would spend an average of $1,078 on prom, including costs for outfits, hair, makeup and manicures. The Dwight-Englewood girls wearing haute designers like Alice Temperley and Roberto Cavalli almost certainly spent much more, while many students from Joplin High School in Joplin, Mo.—the site of a devastating tornado a little over a year ago—arrived at prom in donated attire.
Proms represent other rites of passage too. On May 19 in Massachusetts, the Boston Alliance of Gay, Lesbian, Bisexual and Transgender Youth hosted its 32nd annual prom—the nation’s oldest for GLBT youth—10 days after Barack Obama became the first U.S. president to endorse gay marriage.
“I love the ritual, the time, effort and thought about every detail of preparation to put their best foot forward,” says Laub about documenting proms. “It’s a moment in their lives of transition and hope.” For the students, yes, and perhaps for their schools and communities, too.
Gillian Laub is a photographer based in New York and a frequent contributor to TIME. See more of her work here.