>Am I missing something?

Apparently. >>Since when does the county have anything to do with state registration and state inspections?

Since 1984, your county of registration has determined whether your vehicle is subject to emissions inspection or not. >>> AFAIK, what county you file the paperwork in is irrelevant, and state inspections are required and enforced in every county in Pennsylvania.

The county where your vehicle is registered determines whether or not it is subject to emissions inspection. All cars and light trucks, other than those tagged as farm vehicles, are required to have an annual safety inspection regardless of the county they're registered in.

You're right in that the paperwork can be filed in any county. For example, someone from Chester County could buy a vehicle in Potter County and file the registration/title paperwork in Potter County. His car would still be subject to emissions testing, because he lives in Chester County and the car is registered to his home address.

Drivecleanpa has all the info you could possibly need on this topic.