Yes, Cascade County Zoning Regulations (CCZR) requires all signs, structures, foundations, buildings, and changes of use to obtain a permit with Cascade County Planning Department, as mention in CCZR §9.2.1 under Permits Authorized:
Pursuant to MCA §76-2-207, a Location/Conformance Permit shall be required for all proposed buildings, structures, signs, land uses, and changes in land use within the Zoning Jurisdictional Area except where exempted under Section 9.2.3. Legal Location/Conformance Permits shall be approved and authorized by the Zoning Administrator. A separate Location/Conformance Permit shall be issued for each tract of land and for each distinct use in a project proposal.
To find more information on regulations regarding signs in Cascade County, please check our Cascade County Zoning Regulations §8.1 "Uses, Signs, Lots".