Insurance rates are usually determined based on how likely you are to file a claim.
States with larger populations usually pay more for insurance than states which are less populated. Car insurance companies base this on the fact that in areas with more people, there are naturally more cars and congestion boosting the possibility of having an accident. Also, it matters whether you live in the city center or the suburbs.
Another factor regarding location is rate of auto theft in your area. This factors in significantly if you carry comprehensive car insurance, which is typically covered under such a policy. Obviously, if you have anti-theft devices on your car, this can mitigate some of that theft risk but your premiums will still take a hit because car theft is completely preventable.
Some states have passed legislation that says car insurance companies cannot charge more simply because you live in one area of the country versus another.