Wizard Constable takes place in the small empire of Etrombia, primarily in its capital and largest city, Vaggert, a trading port on its south coast. Etrombia finds itself in a balancing act – it's a small kingdom between two larger ones, and thus is careful and polite in its foreign relations. To the southwest, the country of Parlund outlaws magic, while to the east, Zargrona is run by wizards (the ability to do magic is a rare, often inherited trait). Etrombia has a strong tradition of not allowing wizards to rule the country; it honors wizards and takes advantage of their talents, but the government is run by non-wizards ("simples"). There is a wizard on the Etrombian ruling council, but the rest of the council are nobles and military men. (Luckily for the reader, we only get to meet this council second-hand. It's a dull group.)
The wizards of Etrombia control the weather in the area around Vaggert, ensuring a good climate all year 'round in the city and nearby farms. This control starts at the south edge of the city and extends many miles to the north.
The Empire of Etrombia was originally a number of smaller kingdoms; about 80 to 100 years ago the smaller kingdoms allied with Etrombia, or fell to Etrombia in war. Now the Empire is the only legitimate political body between the nearly impassable Lizard's Teeth mountains to the west, and the Zargonan Desert to the east. But it's still smaller than either of its nearest neighbors.