Route 38 at night only.
You can get Growlithe on Soul Silver. I found mine at route 38.
In SS can you get him at route 37 and 38
Rout 38 is the best option
Route 38 in the evening
I found mine in route 38
I think its in route 37 or 38 but other wise you could trade
You can get growlithe on the poke walker nd route volcano path and at route 36, 37 and 38.
You can find him in route 36, 37 and 38 I found mine a route 37 or you could trade it
Trading It. Remember Some Pokemon don't appear in your version, the same way as with mine. I have one I found it after catching SUDOWOODO on a piece of Grass before Eucrateak. By the way I'm using HeartGold that's how I got one
Growlithe is found only in Routes 36 and 37 in HeartGold. Sorry.
Growlithe is not available in SS, you have to trade him from a HG or the internet.