Sanjo City is the D-Team's home town, located on the central eastern coast of Japan. It remained unnamed until episode 48, when the newswoman reported its name during the Black T-Rex attack. It is the home of several other major locations, like Max's house and the D-Lab.
It is the site of a number of dinosaur occurrences throughout the series.
The forest next to the city is where the Lightning, Wind, and Grass Stones crashed alongside Chomp's card in episode 1. A nearby TV station is where Utahraptor appeared in episode 7, and its subway tunnels is where Ankylosaurus activated in episode 9. Jonathan had the card-folio with Ceratosaurus in the Mega Mall in episode 10, and the Alpha Gang tried using Alpha Acrocanthosaurus to attack the city in episode 16 to get back the D-Team's dinosaur cards.
A nearby cave was where Euoplocephalus activated in episode 21, and a nearby airport for Megaraptor in episode 22. The Alpha Gang doppelgangers tried robbing the local bank in episode 26, and the real Alpha Gang took over and reopened the city's old amusement park when they needed money in episode 27. The Alpha Gang also took over a local ironwork in episode 36 to refine a sample of Alpha Metal.
Rod and Laura went to Sanjo City to get into Max's house and try to take back the D-Team's dinosaur cards again in episode 45, the Alpha trio soon getting sent after them with Megalosaurus. Seth flew the Backlander here to give the Black T-Rex a test run in episode 48, and remained over the city in the season finale as the D-Team and Alpha Gang fought to defeat the dinosaur.
Seth escaped to present day Sanjo City with the Black Cosmos Stone in episode 78 to hold Reese, Dr. Owen, and Patrick ransom at the D-Lab to bring the D-Team to him, with a surprise attack by Spectre merging the Cosmos Stones into the Dark Pterosaur, which floated over the city in the series finale as the D-Team and Alpha Gang tried to destroy it.
- Unlike many English-dubbed anime, which attempt to "localize" the setting from Japan to America, Dinosaur King leaves in every map and reference to allow the D-Team's home to remain obviously in Japan. The excessive use of maps showing dinosaur appearance locations may have forced 4Kids to leave the location unchanged to avoid confusion and criticism, or simply to save effort on editing them all.