Grounding Rod Requirements - Washington State?

[RogerPDX]

I have a new ground wire from my panel to the outside that needs a grounding rod.
I went to Home Depot to buy one and noticed that they come in a variety of diameters and lengths.
What diameter & length should I use (legally) for a 200 amp service?
I saw:
1/2"
5/8"
3/4"
8' length
10' length
Rods are available in both copper clad & galvanized.

Thanks for your input.

 

[WorthFlorida]

http://www.nfpa.org/codes-and-stand...-of-codes-and-standards/free-access?mode=view

Click on this link and forward to page 136 of 940.