WMI Code allocations by city #database
The first three characters uniquely identify the manufacturer of the vehicle using the World Manufacturer Identifier or WMI code. A manufacturer that builds fewer than 900 vehicles per year uses a 9 as the third digit and the 12th, 13th and 14th position of the VIN for a second part of the identification. Some manufacturers use the third character as a code for a vehicle category (e.g., bus or truck), a division within a manufacturer, or both. For example, within 1G (assigned to General Motors in the United States), 1G1 represents Chevrolet passenger cars; 1G2, Pontiac passenger cars; and 1GC, Chevrolet trucks.
You can download this database for free from ftp://ftp.nhtsa.dot.gov/manufacture/manufacturer.mdb