1. They issued all their phone numbers according to a geographic system, the North American Numbering Plan. Most cities would have one prefix, some larger ones gradually needed two or more, but basically you can tell from a number if the call is local.
2. Calls to local numbers were cheap or free, because routing a call on a circuit a few miles costs essentially nothing. Just spread the cost over all subscribers, it's fine.
3. Mobile telephones exist. NANP is full. How do we number these new phones? Let's give them local numbers wherever you're buying the phone.
4. Oh, but calls for a mobile cost more. Do we make everybody pay extra for the small fraction with mobiles? No. Can we charge callers for calling a mobile? They'd have no way to know they're getting charged because the numbers are local! OK, so let's charge _mobile owners_ when they receive a call.
5. Then everybody buys a mobile phone.
The end state is always the same, everybody eats the cost of maintaining a network and calls are basically free. But the way they got there was different from most countries.
