Which car insurance companies are based in Pennsylvania?

There aren't many major car insurance companies *headquartered* in Pennsylvania. Most large insurers are nationally or internationally based. You'll find many *operating* in Pennsylvania, but their headquarters are elsewhere.

To find companies that might have a significant Pennsylvania presence (regional offices, etc.), you'd need to research insurance companies doing business in PA and then look at their "About Us" sections on their websites to see where their main offices are located. This is difficult to do comprehensively without extensive research.