From Fotomat booths to typewriter erasers, many things that were common a few decades ago have been phased out by new technology. The reason for the disappearance of white dog poop, however, is less obvious. It wasn't a product of your young imagination: Chalky, white dog poop really was everywhere in the 1970s and '80s. It started to become a rarer sight in the 1990s, and today, it's practically nonexistent. Dogs are still doing their business as much as they were 30 years ago, but thanks to changes in pet food formulas, what comes out has changed.
According to Treehugger, the culprit behind the white dog waste of the past was a surplus in calcium. Dog food used to contain an overabundance of meat and bone meal, both of which are high in the mineral. Whatever the dog couldn't process ended up in its feces, and as the wet matter dried out in the sun, the hard calcium stuck around. This led to crumbly, mummified turds littering our sidewalks and green spaces.
Today, commercial pet food brands are less likely to rely on bone meal for cheap filler. They've added more fiber to their products and lowered the calcium content. The result is healthier, more-naturally looking waste from the general dog population.
It's still possible for dogs to get too much calcium in their diet in the 21st century, so white dog poop hasn't gone away for good. Because it's rare, you should notify your vet anytime you see discoloration in your pet's stool. White specks in dog poop could be a sign of a more serious problem like worms.