The night sky is disappearing. Growing cities and towns pump more artificial light into the sky all the time. That creates a glowing dome that blots out the view of the Milky Way, meteors, and other beautiful but faint sights.

Light pollution does more than make it impossible to appreciate the beauty of the night sky. It can interfere with the migrations of many animals, and it can harm human health. And it wastes energy by shining light into the sky instead of onto the ground, where it’s needed.

In recent decades, though, some places have tried to limit the light pollution. They’ve passed laws that restrict outdoor lighting, keeping the sky as dark as possible. An international organization certifies the most successful ones. And number one on the list was Flagstaff, Arizona. It was declared the first International Dark-Sky City 25 years ago this week.

Flagstaff began protecting the night in 1958. Lowell Observatory was adding a big new telescope, and it needed dark skies to get the best results. So the city placed restrictions on outdoor lighting. As the city grew over the following years, it beefed up those regulations, winning certification in 2001.

Today, there are more than 60 dark-sky communities, plus dozens of dark-sky parks, reserves, and other sites. That includes a wide swath of West Texas, which is home to McDonald Observatory. These locations help keep the night sky from disappearing.

Script by Damond Benningfield