The following is from the Montana Legislative Website.
FIND A MONTANA LEGISLATOR
Not sure who represents you in the Montana Legislature? Need to know how to contact your legislator?
Here are some ways to find a Montana legislator:
By Address: View a map for which any Montana address can be entered to find legislator and district information.
By Name: Find information on your legislator by Session year on the the Legislator Roster.
County Elections Office: Staff of your county election office can help you determine which legislative district you live in and who your representatives are. The Montana Secretary of State's Office includes contact information for county election offices on its website.