The Sierra Club is the nation’s largest grassroots environmental organization—and also one of its oldest. On this date (May 28) 125 years ago, a small group of people gathered in a lawyer’s office in San Francisco to establish what would become one of the United States’ most effective advocacy groups.

While we here at the Sierra Club are proud of what the organization has accomplished in more than a century of fighting for clean air, clean water, and wild places, we’re equally proud that we still have the energy of a 25-year-old. Now more than ever, we’re working tirelessly to promote a transition from a dirty energy to clean energy; to defend our public lands and the wondrous critters that live there; and to give people access to natural areas.

Even as we keep our ambitions focused forward, it’s important to remember the past—and how we’ve grown and evolved over the last 125 years. In case you missed it, please check out Rebecca Solnit’s inspiring and thoughtful essay about the Sierra Club’s history. Then take some time to check out this slideshow of old Sierra Club photos gleaned from our Colby Library.

Mostly you’ll notice how things have changed. Today’s hiking and climbing gear is much better than it used to be. The ranks of wilderness lovers aren’t so lily-white (even though the effort to create a conservation movement that reflects this nation’s amazing diversity is still very much a work in progress). 

But look closely and you might also see how things have remained the same. Today, just like a century ago, the Sierra Club is committed to introducing people to the thrills and rewards of exploring the natural world. If a 125-year history has taught us anything, it has confirmed our belief that people will only work to defend what they know and love. So once you’ve scrolled through all of these photos, please shut off your computer, go outside, and enjoy.