I'm sorry, I forgot Port Wakefield, though in working on memory I would have said it was inaugurated in 1954, a year or so before the AGP there in 1955...

Are you in Australia?

Yes, in the main, airstrip circuits had a triangle to work with. But not Mt Druitt, nor Marsden Park, Strathpine, Lowood, Point Cook, Mooliabeenie, Ringwood, Tomago, Gawler, Beverley or Quorn Hall. So I guess it's not even 'in the main' when you count them up. Then you look at some, like Schofields and the main Caversham circuit, they had the triangle but didn't use it, racing in part on taxiways etc.