Was the triceratops the last dinosaur to live on earth?

We don't know for sure, but it's very possible. It certainly was large enough and strong enough to defend itself, at ten feet high at the hip, thirty feet long, and ten tons. Of course, its fearsome-looking head and three-foot horns would have meant that only the most desperate of carnivores would have tried to attack it as an adult. It's also unique in the fact that its teeth were meant for grinding. That, coupled with a powerful beak, probably meant that it could eat a wide variety of plants in times of crisis. Although it was slower than most carnivores (Its stubby legs prevented it from running faster than 15 miles per hour), it could certainly hold its ground. As long as it could survive the initial ejecta blast from the asteroid, it's likely we would have seen them long after the last Tyrannosaurs and Hadrosaurs died.

It should also be noted that, if the above is true, Triceratops would have been the last non-avian dinosaur- a group which included most of the dinosaurs mentioned in coffee-table books. However, another group of dinosaurs, the avians, split off during the Jurassic to eventually evolve into modern birds. They were just as successful in every way the dinosaurs were and more. So, in a way, you could say that your average farmyard chicken is the last dinosaur.