Nick Nixon’s annual photographs of his wife, Bebe, and her three sisters chart the psychological and physical processes of maturation and aging and record the bonds of sisterhood. When Nixon made his first successful picture of the four sisters in July 1975, Bebe (Beverly Brown) was 25, her sister Heather was 23, Laurie was 21, and Mimi was 15. A year later, in June 1976, the sisters gathered again for Laurie’s college graduation. “And that’s when I took the second one,” Nixon later recalled, “and kind of on a whim, said let’s do it in the same order. So it was having two pictures in my hand, and the year space between them that gave me the idea that it would be really interesting to do it forever. And so I asked them if we could. And they all laughed at me and said sure.” For 39 years now, the sisters have stood before Nixon’s camera, always in the same order—Heather, Mimi, Bebe, Laurie—for what has become a courageous “annual rite of passage.” From the dozen or more negatives that Nixon shoots each year, he chooses a single image as the latest installment in the series.

For The Brown Sisters and all of his work, Nixon bucked the trend of handheld, shoot-from-the-hip photography prevalent in the 1970s by opting instead for a tripod-mounted, large-format camera that produced 8 x 10-inch negatives. His photographs, contact-printed so that there is no loss of detail through enlargement, are intimate in scale but filled with visual information.

Returning years later to rephotograph a portrait subject has become a common trope in fine art photography and even an Internet meme among amateurs, but the early date and uninterrupted continuity of Nixon’s project sets it apart. The subtlety and sensitivity that mark The Brown Sisters could only come from the connection between an exceptional photographer and trusting subjects. “Being an only child, it was really gratifying and lovely to be embraced by this family,” Nixon has said. “There’s still a ground water of affection and support. I look back at these thirty-some pictures and it’s like they’re of my sisters. I can feel myself getting old with them. And I’m part of them; they’re part of my love.”