The answer to this question is quite simple. There are really three major factors.
The most obvious factor is that some states simply have a higher rate of accident for one reason or another. For example, New Jersey is extremely congested, and because there are more cars on the road, there is a higher chance of accident. But congested states aren’t the only ones with high accident rates. Some states with high deer populations or other animal wildlife may have high rates of automobile damage, which will cause the insurance companies to build these factors into the price of your car insurance.