My son was born at ontario, I was told I need to pick up his birth certificate, do I pick it up there or does the county building have it

You need to go at city hall record

At the county office

The County Birth Records Office will have the copy.

County Register recorder

You may want to call them (Kaiser) and ask, I'm not sure.

You have to send paperwork Kaiser given you to the county in which your born was in.