Boise Rep. Cherie Buckner-Webb said on her Facebook page that she received the hand-written mailing at her home address.
"Check out communiqu from the KKK received this week in the mail," Buckner-Webb said in a post. "Newsletter, Application...Really?"
The local lawmaker posted a photo of the KKK application which asks folks to pay a $35 annual fee and proclaim that "I am a white Christian man or woman. I am not married to a nonwhite. I do not date non-whites nor do I have nonwhite dependents."
"(It) was addressed by hand," she said in a follow-up post. "Something a little unsettling."
Buckner-Webb told her Facebook followers that she vowed to remain vigilant and wants to move forward.
"On to new topics and positive action to improve our communities," she said.