The majority of the dinosaurs that were herbivores had very long necks so that they could reach the leaves that their diet mainly consisted of. This was true for the Brachiosaurus perhaps more than any other dinosaur. The Brachiosaurus had an elevated front processing both long front legs and a very long neck.
These attributes paired with a large body, shorter hind legs and a shorter tail gave this dinosaur the leverage it needed to reach high into trees for its source of food. The Brachiosaurus lived in North America in what is now Colorado. The ample vegetation in this area served this dinosaur very well as a food source.