Detectives executed search warrants at a home in the 1700 block of 18th Avenue in Clarkston and a home in the 200 block of South Star Avenue in Lacrosse.
In Clarkston, detectives found packaged meth and cocaine, and two handguns.
In Lacrosse detectives found cocaine, scales and other packaging materials.
Jessica Young and Donald Hume were arrested in Clarkston, while Theodore McGuire was arrested in Lacrosse.
"We believe that these people were involved in bringing narcotics into our region," said Whitman County Sheriff Brett Myers. "Primarily trafficking them in the Palouse and down into the Valley."
Young and Hume now face possession with intent to deliver meth and cocaine and felony firearm charges, while McGuire faces charges of possession with intent to deliver cocaine.
Detectives are still investigating this case, so there could be additional charges filed.