Here is all the info.
go to the Clay County website:http://www.claycountysd.org/
and then hit the Treasurers Office button.
The contact info is on that page:
211 W. MAIN ST. SUITE 201
VERMILLION, SD 57069
You have to register with Clay county in South Dakota, that is why it is not mentioned on the SD state webpage.
I got everything together and then called the office and the lady gave me how much I would owe them for the first registration, as it is pro-rated. Everyone has a renewal month based on the first letter of their last name, so you will pay for the first registration that covers up until your renewal month, then have to pay for the next whole year thereafter. After the first time, you can register to pay online.
They were very small town friendly and helpful. They have no problem with us living here in Mexico and having an address in another state.